Hey @GEF, I think it's time to give Biktrix a call. I assume both batteries work fine in the lower battery position, correct?
A poorly seating upper battery due to the frame or connector misalignment sounds like a major issue.
Yeah, the chat operator on the weekend isn't a mechanic but referred my question. Yes, both batteries work fine on lower slot, either needs to be jammed into upper slot. With effort I can hold it down and get the slider into position, but there's still a gap at the high end of the slot. When the battery is out and I inspect the electrical connection it looks just like the lower one, but it must not fit. For now battery is secure but I've heard Biktrix has excellent post-sale support. That was a factor in my decision and now I hope it was justified. -GEF