Yep, as Gar said, the Omron should be all that is needed for filtering and ride through of line side glitches. It's an inexpensive part if you suspect it may be bad. They don't last forever. Omron, Meanwell are good brands.
I would suggest further information gathering is necessary. What is failing and the failure mode. If the control boards are getting blown, it could be something at the input or someting at its outputs.
If it will just not regulate temp, often that's a standalone PID temp controller, and they also do not last forever. Maybe bad connection between it and the sensor, bad sensor ... A standalone PID temp controller probably takes line voltage, not loaded on the Omron.
Is it used with some kind of warranty, factory refurbished, or auction equipment used?
Are they blaming, suspecting, bad line voltage or is it possible the equipment was just liquidated and moved from somewere else without concern it actually runs. There is a question of who is responsible for repairs and diagnosis if the problem is in the equipment.
The 400/230 Y tranny, do you have 400 at the line side to feed it? If you don't, and the load is single phase, it would be pretty easy to get a seperately derived 230 v secondary and ground one side for a neutral, matching system voltage at the primary. If the 400/230 Y matches the application perfectly, take a look at its system bonding jumper (primarily) and GEC. Measure the N to G voltage, resistance, as a quick check to see if its more than expected. The sensitive control boards will not like the N to G voltage more than 1.5 v or so.