I think I figured out more specifics on the issue. On the “web” (not mobile “m.”) version of CB, it appears that when you drag-n-drop a transaction, with repeats, to a different date, the repeats are removed from the change automatically. The mobile version does not have a drag-n-drop capability, so I typically go into the Edit screen for the transaction and change the date, equivalent to drag-n-drop, and save out. The repeat dates are still set, so the “save” action outcome typically asks for the user choice of only “this” transaction, this and future (rebuild/recreate), or all transactions. Normally, I pick the “this” transaction, but every now and then I choose “this and future”. Because the problem that periodically happens to me is with the mobile .m version and appears on certain transactions (with a repeat) and going into the past up until a certain point, but not all past transactions (from a repeat), I believe there must be a conflict of some sort between the transaction settings and the repeat. Without logs to see the final settings of the transaction, I'm unsure of what is truly happening.
Also, I'm testing out the Android app on my phone (just saw it was now available). Looks very nice! I discovered how to right-swipe a transaction to set it to complete or left-swipe to delete. Much easier than long-press on the mobile-web version, which could also be part of the issue I'm experiencing. I could see how long-press could potentially be interpreted oddly between a big fingertip and multiple small boxes (which transaction is selected in the radius of the fingertip?). Make sense?