Subtitle download error

Hi,
I have Kodi on a pi connected to a Synology NAS via nfs. Until recently there has been no errors downloading and using subtitles on Kodi, but within the last few days, this error started to occour:
10:36:21 50746.859375 T:1644164080 ERROR: OnDownloadComplete – Saving of subtitle /home/osmc/.kodi/userdata/addon_data/service.subtitles.opensubtitles/temp/e06c8a6f-4221-4108-af2f-2bd547b046f3.srt to special://temp/nfs://10.0.0.5/volume1/MyFolder/MySub.srt failed

Usualy I would expect some kind of restriction on the destination folder, but that does not seem to be the issue:

sudo cat /etc/exports
/volume1/MyFolder 10.0.0.10(rw,async,no_wdelay,crossmnt,insecure,all_squash,insecure_locks,sec=sys​,anonuid=1024,anongid=100)
/volume1/MyOtherFolder 10.0.0.10(rw,async,no_wdelay,crossmnt,insecure,all_squash,insecure_locks,sec=sys​,anonuid=1024,anongid=100)

My Pi: 10.0.0.10
My NAS: 10.0.0.5

-any ideas?