Can you swap out that dimmer with one of the other dimmers in that box to see if the problem stays with the circuit or follows the switch?
And as a follow up question to the previous, does the dimmer update correctly when using the dumb switches?
The only similar issues I have read about also seem to include issues with the dumb switches as well, and especially when wired with no neutral. Whether or not this is the same root issue, I don’t know.
The fix that I am aware of is to install the latest beta firmware and make adjustments to the new “Dumb Detection Level”. Even though you aren’t having issues with the dumb switches, it’s possible the dimmer is having a problem determining which traveler is carrying the load.
Again, I don’t know that this is the issue you are having, so not sure if this will work for you.
I think that this is ultimately the issue, where it would likely work fine in a 3-way setup with a single dumb switch, it’s possible that in a 4-way setup with 2 dumb switches is just causing that much of an issue. Again, this might be fixed with the latest beta firmware installed on that switch and the “dumb detection level” cranked up, but I can’t be certain.
So long as you have the Line from the panel feeding the dimmer, which there would be other issues if you didn’t, then you’re likely fine.
It’s possible that this wouldn’t be an issue with Aux switches and effectively fix this problem, but there is also a similar issue with those, again, mainly on no neutral connections though. The fix is basically the same, get the newest beta firmware and adjust the “aux detection level” instead.