Deceleration when hybrid meter is low

Update: The issue below ONLY happens if the hybrid battery indicator shows its level at its lowest. I have found that by switching to "recharge mode" before even getting to the hybrid system, this does not occur. Wondering if this might indicate where the trouble is!

I have a 2017 Prime and have developed an issue that stumped the dealership techs. It's happened about 6 times over the past two months while at high freeway speeds. Suddenly, it's as if I'm in neutral, but I'm not. Energy output is into the red and everything looks normal on the dashboard, but no acceleration at all. I have panic flipped my gear shift nob into neutral and then back to drive a few times and eventually it comes back, but not before losing 25mph or so of speed. No warnings showing up nor is there a record when the dealer checks the computer, but it's a legit problem! Forever grateful if anyone has any insights! (Note: I think it has only happened in hybrid mode, not while on full electric...