You wrote you are using WebUI.takeFullPageScreenshotAsCheckpoint keyword, which will produce a “full height” screenshot image.
Previously you posted another post: How can I ignore page height for the visual testing to match with existing baseline
where you asked a question
When running my visual testing all my screenshots go to U (Unresolved) because of different page height.
To me, it seems that your target web page changes its full height dynamically. At one time the screenshot image has the height of, for instance, 10082px; and at another time the height changes to 9882px; and at another timing the height could be 10180px. Is it the case?
If 2 PNG files with different height are given, any image comparison library would determine that the 2 files are different. — Are you unhappy with this behavior? What do you what them to behave otherwise?
Are you aware what is the reason why your target web page dynamically changes its height? There might be some HTML element(s) with movable height, which result the full-page height to change. Are you aware which element(s) are the bad factors? I think, you should analyse your target web page in more detail. If you have found out the reason, then you might realize some way to workaround your difficulty for yourself.
I guess that the Katalon’s Visual Testing feature (of Full Page Screenshots) implicitly assumes that the target web page has static width and static height; only the content pixels are to change.
If you can not stop the target web page to change its full-page height dynamically, I think that you should not apply the “Visual Testing” facility to it at all.