Steam Boiler Overfill During Brewing

[espressomaker]

Hi all,
The other day when brewing I noticed my steam boiler overfill by the vacuum breaker. My initial thought was the machine could use a descale as I purchased it used and the previous owner seemed unaware of maintenance but after two descale the issue persists. I noticed that it only occurs during brewing or back flushing but when running water through the group the steam boiler doesn’t overfill. Otherwise all seems functional( other than a broken pressure gauge)
My thoughts are that
1 it is not an issue with the autofill system because it only happens when brewing
2 the increased pressure from brewing is causing back flow
My amateur internet sleuthing led me to a component called the inlet solenoids valve.
Does it make sense that this is the culprit?
Or should I check elsewhere?
Any and all help is appreciated!

[espressomaker]

Just to post an update I successfully cleaned the steam boiler fill valve; there was a small piece of scale or something by the seal. And also have successfully switched out the gauge for the one from espresso parts
One note tho is it an issue that I am using a push to connect made for pneumatic air systems to connethe steam pressure gauge portion