AzCopy fails to copy/sync *some* files saying no PUT permission

Question

We need to sync files between two Azure File Shares. We use SAS tokens to let azcopy access both sides. Out of 126 files at source, only 122 have been synced, for others we get following error:

INFO: Authentication failed, it is either not correct, or expired, or does not have the correct permission PUT (here the file path on target File Share)

What we did to troubleshoot:

• regenerating SAS tokens (didn't work), we generate the through portal
• changing file name on source - for one file it worked, file was copied, for other file it didn't...
• the same issue happens for copy and sync commands

For now we are really disappointed with how this tool is working. Any ideas what might be wrong?