Hi,
It appears that all the image URLs are rendered within the href attribute of the gallery, thus a click isn't even necessary. I added the images selector to the sitemap, give it a try.
{"_id":"matrix","startUrl":["https://matrix.abor.com/Matrix/Public/Portal.aspx?ID=DE-271449725372&eml=ZmFpemFuQGxldGh1Yi5jbw==#1"],"selectors":[{"clickActionType":"real","clickElementSelector":"div.multiLineDisplay .d-fontSize--largest a","clickElementUniquenessType":"uniqueCSSSelector","clickType":"clickOnce","delay":2000,"discardInitialElements":"discard-when-click-element-exists","id":"listing-click","multiple":true,"parentSelectors":["_root"],"selector":"html","type":"SelectorElementClick"},{"id":"properties","multiple":true,"parentSelectors":["listing-click"],"selector":"_parent_","type":"SelectorElement"},{"clickActionType":"real","clickElementSelector":"span.image a","clickElementUniquenessType":"uniqueCSSSelector","clickType":"clickOnce","delay":1000,"discardInitialElements":"do-not-discard","id":"imageSlider","multiple":false,"parentSelectors":["properties"],"selector":"_parent_","type":"SelectorElementClick"},{"id":"propertyName","multiple":false,"parentSelectors":["properties"],"regex":"","selector":".d-mega span","type":"SelectorText"},{"id":"address","multiple":false,"parentSelectors":["properties"],"regex":"","selector":".d-textSoft span","type":"SelectorText"},{"id":"rent","multiple":false,"parentSelectors":["properties"],"regex":"","selector":"span.d-fontSize--largest","type":"SelectorText"},{"id":"description","multiple":false,"parentSelectors":["properties"],"regex":"","selector":"span.d-textSoft","type":"SelectorText"},{"id":"petPolicy","multiple":false,"parentSelectors":["properties"],"regex":"","selector":"div:nth-of-type(25) span.d-text","type":"SelectorText"},{"id":"availabilityDate","multiple":false,"parentSelectors":["properties"],"regex":"","selector":"div:nth-of-type(22) div.col-xs-12:nth-of-type(1) span.d-text","type":"SelectorText"},{"id":"applicationFee","multiple":false,"parentSelectors":["properties"],"regex":"","selector":"div:nth-of-type(22) div:nth-of-type(3) span.d-text","type":"SelectorText"},{"id":"applyNow","multiple":false,"parentSelectors":["properties"],"regex":"","selector":"div:nth-of-type(22) div:nth-of-type(11) span.d-text","type":"SelectorText"},{"id":"parking","multiple":false,"parentSelectors":["properties"],"regex":"","selector":"div.row:nth-of-type(5) div:nth-of-type(3) span.d-paddingLeft--6","type":"SelectorText"},{"id":"headerImage","multiple":false,"parentSelectors":["properties"],"selector":"img.IV_Image","type":"SelectorImage"},{"id":"propDetails","multiple":false,"parentSelectors":["properties"],"regex":"","selector":".d-borderWidthLeft--1 > div:nth-of-type(2) > div:nth-of-type(2)","type":"SelectorText"},{"id":"how_to_apply","multiple":false,"parentSelectors":["properties"],"regex":"","selector":"div:nth-of-type(22) div.col-sm-12","type":"SelectorText"},{"extractAttribute":"href","id":"images","multiple":false,"parentSelectors":["properties"],"selector":".image a","type":"SelectorElementAttribute"},{"clickActionType":"real","clickElementSelector":"button#_ctl0_m_btnClosePILP","clickElementUniquenessType":"uniqueCSSSelector","clickType":"clickOnce","delay":2000,"discardInitialElements":"do-not-discard","id":"close","multiple":false,"parentSelectors":["properties"],"selector":"_parent_","type":"SelectorElementClick"},{"clickActionType":"real","clickElementSelector":"button.right","clickElementUniquenessType":"uniqueCSSSelector","clickType":"clickOnce","delay":0,"discardInitialElements":"do-not-discard","id":"click1","multiple":false,"parentSelectors":["imageSlider"],"selector":"div.mtx-modal-body-sx","type":"SelectorElementClick"},{"clickActionType":"real","clickElementSelector":"button.right","clickElementUniquenessType":"uniqueCSSSelector","clickType":"clickOnce","delay":0,"discardInitialElements":"do-not-discard","id":"click2","multiple":false,"parentSelectors":["imageSlider"],"selector":"div.mtx-modal-body-sx","type":"SelectorElementClick"},{"clickActionType":"real","clickElementSelector":"button.right","clickElementUniquenessType":"uniqueCSSSelector","clickType":"clickOnce","delay":0,"discardInitialElements":"do-not-discard","id":"click3","multiple":false,"parentSelectors":["imageSlider"],"selector":"div.mtx-modal-body-sx","type":"SelectorElementClick"},{"clickActionType":"real","clickElementSelector":"button.right","clickElementUniquenessType":"uniqueCSSSelector","clickType":"clickOnce","delay":0,"discardInitialElements":"do-not-discard","id":"click4","multiple":false,"parentSelectors":["imageSlider"],"selector":"div.mtx-modal-body-sx","type":"SelectorElementClick"},{"clickActionType":"real","clickElementSelector":"button.right","clickElementUniquenessType":"uniqueCSSSelector","clickType":"clickOnce","delay":0,"discardInitialElements":"do-not-discard","id":"click5","multiple":false,"parentSelectors":["imageSlider"],"selector":"div.mtx-modal-body-sx","type":"SelectorElementClick"},{"clickActionType":"real","clickElementSelector":"button.right","clickElementUniquenessType":"uniqueCSSSelector","clickType":"clickOnce","delay":0,"discardInitialElements":"do-not-discard","id":"click6","multiple":false,"parentSelectors":["imageSlider"],"selector":"div.mtx-modal-body-sx","type":"SelectorElementClick"},{"clickActionType":"real","clickElementSelector":"button.right","clickElementUniquenessType":"uniqueCSSSelector","clickType":"clickOnce","delay":0,"discardInitialElements":"do-not-discard","id":"click7","multiple":false,"parentSelectors":["imageSlider"],"selector":"div.mtx-modal-body-sx","type":"SelectorElementClick"},{"clickActionType":"real","clickElementSelector":"button.right","clickElementUniquenessType":"uniqueCSSSelector","clickType":"clickOnce","delay":0,"discardInitialElements":"do-not-discard","id":"click8","multiple":false,"parentSelectors":["imageSlider"],"selector":"div.mtx-modal-body-sx","type":"SelectorElementClick"},{"clickActionType":"real","clickElementSelector":"button.right","clickElementUniquenessType":"uniqueCSSSelector","clickType":"clickOnce","delay":0,"discardInitialElements":"do-not-discard","id":"click9","multiple":false,"parentSelectors":["imageSlider"],"selector":"div.mtx-modal-body-sx","type":"SelectorElementClick"},{"clickActionType":"real","clickElementSelector":"button.right","clickElementUniquenessType":"uniqueCSSSelector","clickType":"clickOnce","delay":0,"discardInitialElements":"do-not-discard","id":"click10","multiple":false,"parentSelectors":["imageSlider"],"selector":"div.mtx-modal-body-sx","type":"SelectorElementClick"},{"clickActionType":"real","clickElementSelector":"button.right","clickElementUniquenessType":"uniqueCSSSelector","clickType":"clickOnce","delay":0,"discardInitialElements":"do-not-discard","id":"click11","multiple":false,"parentSelectors":["imageSlider"],"selector":"div.mtx-modal-body-sx","type":"SelectorElementClick"},{"extractAttribute":"src","id":"image-urls","parentSelectors":["imageSlider"],"selector":".j-imageRow:nth-of-type(-n+15) img","type":"SelectorGroup"},{"clickActionType":"real","clickElementSelector":"div.close","clickElementUniquenessType":"uniqueCSSSelector","clickType":"clickOnce","delay":1000,"discardInitialElements":"do-not-discard","id":"close-slider","multiple":false,"parentSelectors":["imageSlider"],"selector":"_parent_","type":"SelectorElementClick"}]}