Never have heard of this problem before.
It would really be helpful if your posts would indicate what image and version you are running. As you know, the E2 images and versions can be quite different and some are very buggy.
Run TNAP 3.2 image almost exclusively and have not observed the SNR meter to lock-up.
I suppose the automatic tune and focus process might be problematic if selecting a transponder that has a similar parameters on a nearby satellite, but that is only a guess. Maybe see if it happens if using specific transponders?
I rarely use the positioner set-up screen as I optimize dish position and skew much faster (10-15 seconds) than the automated sweep and peak process. It is a fun feature that most STBs don't have, but I don't have the patience for the automated function process.