I tend to have different-looking arrows on my system when viewing symlinks, hard links, and junctions. In my case, those arrows are made by a shell extension called “Link Shell Extension”. In my case, the arrows look different, but I might be using an old version (I don’t boot into Windows very often, so I don’t update often). If you have Link Shell Extension, or any similar shell extensions, that might be your problem.
PS: I agree with @gonca:
I quite honestly doubt the issue has anything to do with 7-Zip.