Intermittent Oil Burner Issue

I have an odd intermittent issue my oil burner. I’m looking for some insight.

First, some details. It is a 14-year-old Weil-McLain Series 3 Gold water boiler with a Riello 40 Series burner. It is controlled by a Hydrostat 3150 aquastat (Set L-155, H-180, Diff-10).

Now onto the problem. Periodically, the burner will not fire when the low temp is reached. It doesn’t try and fail to ignite; it seems like there is never an attempt. Sometimes this happens once every two weeks but there have been days where it happened four times in one day. The Hydrostat has a digital readout so I can see the temp is below 145.

It also mostly appears to happen when using hot water, the call for heat for the hydronic baseboard heating seems to be mostly fine, maybe once or twice. This was first encountered on Christmas Eve 2023. I turned the service switch off and then back on and the burner fire immediately. This happened on and off until mid-March of this year when I got fed up. I did some base troubleshooting by checking the voltage and contacts, which appeared to spec. I also checked and reset the high and low limits.

I though the resetting of the temps was the trick as things had been running fine until two days ago when the same symptoms returned. Was washing dishes and the water got cold. I checked the garage and alas, the temp was 120. One push of the button and we’re back in business until yesterday, and then again today.

Also back in March, I had our usual tech out to take a look at he said since everything was working, just changing the aquastat was an expensive gamble.

Is it time to replace the aquastat? Is there anything else that could be the culprit? Any and all thoughts are welcome and appreciated.