User can`t access files on share despite correct permissions

Question

Dear Community,

i am having the following problem:

A user tries to access files on a share for which he has the proper permissions but always gets access denied error. We have a permission group for that folder with 20 other users in it that all can access the files. View effective access on the folder for that user says everything is fine. I checked with gpresult /r that the userprofile is in fact a member of the group and his userprofile is not damaged in any way i could tell.
I don't know what else i could check.