Perhaps this would be helpful... The Denver effect?

NoStream wrote:Ideally, you'd measure with a Scace device. Short of that, you can probably jam a thermocouple into the portafilter to get a more accurate reading - or at least collect the water in a low heat capacity vessel (metal or plastic cup).

I think the BDB measures temperature at the boiler, so you wouldn't expect grouphead temp to match the readout unless there's an offset to compensate.

Phil Mcknight said in a forum post a long time ago (can't remember if it was here at HB or not), something to the effect that (if I understood him correctly) the offset is built in. He said they iterated the display using a Scace, so that what is in the display is what you would read on a Scace. I don't know the intricacies of offset that might foil that scheme.

Somewhere in one of these threads, he or someone posted Breville's actual results from a Scace test of a BDB. Pretty impressive, if they are to be believed. But then, also in line with other people's Scace testing of the BDB.

Here's a quick and dirty Scace job I found on youtube. Not a comprehensive Scace test: -Peter

DaveB wrote:Besides having a PID for both the steam boiler and the brew boiler, the BDB also has a PID for the group head to control the temp, which is heated independently of the boilers by means of a heating element inside the group head.

Very cool. Between your post and pcrussell's, it seems safe to say that a BDB should deliver its claimed temp at the grouphead if operating correctly.

One could speculate that higher elevation would lead to more aggressive offgassing or slightly different bean aging... But 3,500 feet isn't that high.

Well I may have "solved" it.
By solved I mean, I may have overlooked the most simple solution.
I unplugged the machine for a few hours, then did a reset to default settings.
Now things seem to be working as per usual.

Thanks for all of the suggestions from everyone who chimed in though!

noisewater wrote:I unplugged the machine for a few hours, then did a reset to default settings.
Now things seem to be working as per usual.

After other methods failed, I was able to get rid of the pesky Descale prompt by unplugging the machine for 10 minutes and then doing a reset, so it might not be necessary to have it unplugged longer than that.