I posted earlier in this thread, but seem to have resolved my issue for now.
2017 Edge, Europe.
Used the reformat tool quite some time ago, updated to 22251 around christmas.
But recently (last two weeks), I had the same issue with the unit forgetting the settings.
Found this thread, Interrogator utility came up with no free space in /fs/rwdata.
Had a hard time downgrading to the last 3.3 version, unit came up with the VER_ERR08 error. Last stick I made with the utility was a forced downgrade, which went through successfully.
I have just finished a fresh reformat and installation of the lastest 3.4 version, and now have roughly 900M free in /fs/rwdata.
I will regularly check if that folder is running full again - could it be an issue with the 22251 version? The VER_ERR08 and the lost settings came up in a couple of places in the search.