Excuse me. You were right. They were on different filesystem. I assumed that everything is in the same filesystem below /volume1
I tested again, and it works well also with move action.
Thanks for your support.

Have you tried --action hardlink yet? Just to see what happens and to make sure it's on the same filesystem. csaba@nas:~$ filebot -rename /volume1/video/Sorozatok/NCIS.S14E01.720p.HDTV.X264-DIMENSION/ -non-strict --db TheTVDB --format "{plex}" --action hardlink --lang hu --output /volume1/homes ...

1. I didn't try yet.

2. They were on the same filesystem. The mv test was slow because I tried until filebot also worked.
New tests with a 207M file:
mv:
real 0m0.011s
user 0m0.003s
sys 0m0.003s

cp:
real 0m4.197s
user 0m0.005s
sys 0m0.313s

Hi, I use FileBot 4.7.2 on my Synology NAS. As I see "move and rename" action is very slow because it uses "copy&rename then delete original" instead of "move&rename". Example: csaba@nas:~$ filebot -rename /volume1/video/Sorozatok/Igy.Jartam.Anyatokkal.S01-S05 -non-strict --db TheTVDB --format ...