The current logic for linking filebot to bin is broken. You will have to link the executable into bin yourself. It' where all the other synology app packages are.
And where is "where all the other synology app packages are"? Can't find it :(

Update: OK!
For others with the same problem, I think ...

Hi,
same question here. Last week filebot 4.5.6 was running fine on the DS213j and I have used it for renaming my movies:
NAS> java -version
java version "1.8.0_33"
Java(TM) SE Runtime Environment (build 1.8.0_33-b05)
Java HotSpot(TM) Client VM (build 25.33-b05, mixed mode)
NAS> filebot -version ...