An upstream kernel bug[0] means that this VM is in danger of data corruption. The latest bookworm image on Horizon contains a fix, so the easiest thing (for me) is to delete and rebuild the existing VM.
If that proves difficult because you have work invested in the existing VM let me know and I can try a kernel upgrade. A rebuild is definitely the preferred option, though!
[0] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1057843