Created thumbnails on nfs share not readable for others

I have several Kodi instances with a shared MySQL database and a NFS-shared thumbnail directory on my NAS. OSMC on my RPi2 is my primary device, which scans and updates the library automatically every 8 hours.

Everything is working flawlessly, with one minor issue: The thumbnails created by OSMC on the NFS share are not readable for the other Kodi instances (e.g. on my Fire TV), since thumbnails are created by user 10000:10000 with the rights 644:

-rw-r--r--    1 10000    10000        43.4k Oct 11 17:18 9f9fa309.jpg

If I adjust the access rights to 777 on my NAS, all thumbnails are shown correctly on every Kodi instance.

The question is, whether I can change the access rights/owner of the files created on the NFS share by OSMC directly to 777 or is this something I need to configure on the NAS itself?

Many thanks - as always - for your assistance!