Error saving/opening PDF files

We tested reading, modifying and writing PDF using Acrobat Pro DC on M1 Mac Mini (macOS 11.6) connected to Synology NAS (WebDAV). We found no problem.

After setting the log level to VERBOSE, please reproduce the problem and send us the debug log file :

There is no login related credential information in the log files.

Sorry for the inconvenience it may caused.