portability and "sensitive" files

[Admini]

yes, I found out, it is symantec extension that is forcefully installed,
even if I reset the policies, they are forced by the domain/administrators,
so I won't achieve much,
it could be related not so much to cookies but to syncing,
because I've been getting "sync paused" messages often

If possible, you can disable symantec extension and even symantec itself temporarily, and check whether the issue persists.