Just noticed that the DAC board schematic is incomplete, not showing where the 12V supply is originated from. So there's little use in guessing about possible unwanted effects.
I primarily thought about crosstalk from the 230V side, particularly relay contact arcing. If "noise generating" actions are involves with controlling the DAC and resets happen though, there might be in fact an internal problem of the DAC board. But did you cross check by e.g. shorting the cables, operating the light controllers without load etc.?
Fast spikes can be picked up by a cable of some length, you don't need a direct mains connection.