I’ve developed an open-source program for Windows designed to help you identify and avoid file name character limit issues when using Synology NAS Hyper Backup with encrypted files on external devices 
If you’re using eCryptFS, you’ll know (after extensive research 
) that file names are capped at 143 characters, which is just great… This can cause backup failures with frustratingly vague errors.
We encountered this issue ourselves while backing up our few TB 1 mil + files.
This tool was born out of necessity, and I wanted to share it with the community, maybe it helps someone.
You can check out the program here: GitHub Repository
While there are terminal commands to check file limits, I find the GUI much more user-friendly. If you’re curious, here’s a command that might work in Windows CMD:
find ./volume1 -maxdepth 30 | grep -P '\/[^\/]{143,}[^\/]'