2018 Volt Propulsion Power Reduced, Check Engine Light

Hello people was wondering if any of you have any insight on the problem I'm having with my 2018 Gen 2 Volt. A month ago I started seeing occasional stops in charging on a 110V outlet when I'd plug it in at night. I'd wake up and the car charged about halfway and then stopped, displayed the orange/amber-ish color on the dash charging light, and when I'd get in the display would say "unable to charge". This happened about 4 time randomly over the last month, other times it charged fine. 4 days ago it charged fine overnight to 53 miles, I drove it to work about 10 miles, was coming home in the afternoon with about 35 miles left on the electric range as I was pulling up to a light and it abruptly cut off the electric engine and went to ICE. RPMS were either very high or fluctuating all over the place, and the car would not go into electric mode, and it also said "unable to charge" on the engine status display. It was running horribly in ICE mode which it never has before when it's cut over to running in ICE. Usually it's seamless and running smoothly, just a little louder than the electric. I bought this car about a year ago so I'm the second owner. I know the 1st owner sold it to Carmax about 6 months before I bought it. I bought it with about 33k miles on it and I now have 40k. I didn't have any problems for 11 months, it always charged to a minimum of 53 miles, sometimes up to 57-58 during the summer, and it always finished charging with no problems until a month ago. I drove the car straight to my Chevy dealer because I was literally afraid of how it was driving in ICE mode with up and down RPMs and then driving very slow and unresponsive on the way to the dealer. Do you all think this is a high voltage battery issue or something else? My Chevy app said "problem with lithium-ion battery" so I'm assuming that's what it is, but curious as to whether or not it could be something related to the charging system or both that and the battery? The dealer told me that it would be covered under warranty even though I'm not the original owner, does that sound right? I sure hope so! Let me know if any of you have insight on this issue and I really appreciate it!
PS - I did change out the receptacle to an industrial higher-amp rating outlet also just to be sure my wiring was good, and I've used 2 different chargers as well.