[sjl501]

I've been going back and forth with Synology Support. (Meanwhile, still not one single response from Avid...). Synology has been very responsive and helpful, but has not been able to find the cause of the problem. Here is their last response, which sums up their findings. Maybe this will spark an idea with you, or with someone else who comes across this post.

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From Synology:
Since /MASTER/RECORDING/ProTools/_SONGS/songname_v2/pgzrCSQMvgzfCBBB is not a directory and Windows hidden file/folders are visible to Linux-like files systems such as the DSM OS. There is no way for the BTRFS file system or the DSM update to remove an entire directory on its own. My assumption is that the actual path of the file should've been /MASTER/RECORDING/ProTools/_SONGS/songname_v2/songname_v2.ptx/pgzrCSQMvgzfCBBB/ggvsCSQMrmzfCBBB, hence why the file is not found as ProTools has the wrong path.

Windows is fully compatible with AFP so it may not be something that the DSM had created. Also, I don't believe "ggvsCSQMrmzfCBBB:AFP_AfpInfo" is the file name, as the colon ":" is an illegal character in file names. Most likely, "AFP_AfpInfo" is a property/value in the file "ggvsCSQMrmzfCBBB" that is required for a network connection from ProTools. The interesting part with this theory is the host system such as Windows is supposed to be the one that establishes an SMB/AFP connection to the server. This makes me wonder if ProTools is doing its own mapping, which means there could be network connection/mapping related settings in the ProTools that require a reset.

Hate to say this but we are out of ideas at this point. I would suggest contacting ProTools support, at least to get their correct file structure so we can compare it against the directories you have on the NAS. Besides, even if the DSM is at fault here, you will still want to contact ProTools support since they are the only ones who can help you rebuild or repair the ProTools database.