Thanks Woefulrelic. I have titanium heaters, but may look for ones with their own therm. So what are the "best" name and models these days... I've not been keeping track.
So you still have the same issue? Chances are I'll likely have this recurring as well.
I use the jager heaters because they haven't failed me... yet. They probably suffer the same quality deterioration you see in the other eheim products but time will tell.
I have found it reading proper temp 1 time since it stopped working on resets. It fluctuates but spends most of its time reading ~150f on an 83F tank.