+1 on the battery corrosion. I had similar issues on my Creech a few years back and had similar battery damage (actually, not as bad as yours). Swapped out the batts and no change. Could not even fathom that such minimal corrosion could be at fault. Finally, I swapped out boards and *bam* that was the issue.
The problem is that once corrosion starts, it gets UNDER the traces where you really cannot see it. Once there it causes all sorts of crazy issues, including the ones that you've cited.
This should serve as a PSA for getting those batteries OFF the boards!!! $10-15 prevention via remote battery holder and Lithiums....