I have been having gobs of problems with southbend equipment. Most of the problems deal with non ignition on GS and GB series convection ovens. We go out and it is working then we get another call next week. We replace ignition board, HSI and flame sensor then down again. I think southbend has wire warness problems, but they will not admit that. It could be ignition module problems.
On the 3 I personally looked at recently, flame sense current was above 1 microamp. I always push all contact plugs togather.

I had a STRG-5G steamer last year, Gas valve voltage dropped out then came back. This steamer had a new gas valve, module, ignitor and flame senser. I also increased gas pressure. We lost this account over this steamer. (Hate not easily being able to see the flame on this steamer.)

I have a BGLM-40 tilt skillet that is running away. We just changed the thermocouple assembly, highlimit and thermostat board.

Anybody have any help they can offer me. Can't keep changing parts on these things. Southbend is pretty proud of their parts