Relay chattering problem

The whole circuit is redundant so if R45 is 'clipped' ie just cut out of the circuit then it is totally manual.

just need to decide how to terminate the 339 properly, maybe tie pin2 to earth, gets the 30k into the divider and holds the pin low.

I have put a 10u tant on to see what happens before the clipping exercise, want to see if it helps as well.

Grounding pin 5 of the 339 should do the job.

Other considerations aside, I'd use MOVs at appropriate voltage knuckles with low value resistors & medium (.1-.6uF) caps to keep things within bounds.
Didn't know object was functioning & snubbers in place. I'd also o'scope it to look for spikes that would kill the triac. Good Hunting... <<<)))