Ahh thank you so much, i fund the issues, there was indeed a ServerBoot.removeAll; performed earlier on. Removing it and restarting SC a couple of times fixed it.
I guess removeAll shall not be called then. Is there a way to clean the ServerBoot from my own functions without impacting the standard ones? Shall i just keep track of them on my own?
Apparently it was the same issue as here: ERROR: SynthDef system_link_audio_1 not found - #4 by PitchTrebler
Thank you
PS: i cannot mark the answer as solution, i guess since im not OP.