Hi Grumpy - don't worry, I'm leaning toward the same and watching it closely. Part of the underlying issue is .... was the original install bad , if so I probably need to call someone else in. (Install was under previous owner)
After doing some reading, the measurements above appear to indicate that the aquastat is letting the system run too long. Could that cause the issue?
What was supposed to happen:
-Start off at min 140 F
-Diff was set to (~17)
-Shut off at 157
What did happen:
-Shut off at 175 (max)
Points to the aquastat being the problem, right? Assume that no matter how the tank is sized, etc..... letting the system run too long will inevitably cause pressure problems?
If your home is all radiant floor heat, then you'd want temps to run as low as 140.
If you have standard baseboard heat, should be at 180, but 175 will suffice.
My concern, at this point, is whether you modified the correct setting, saying it runs to 175 when you set it to 157 is concerning.
Your boiler is an alpine, pretty high tech - not an old school cast iron clunker.
Open the owner's manual, there should be a customer service/tech support number to call, I'll wager they will not help you beyond basic settings if you're not licensed, but they can probably refer you to a specialist in your area that is certified, or experienced with Burnham Alpine.