I figured the problem. Anyone who has this issue, I know many do. I’ve gotten 2 replacements and both have it.
Apparently it’s not the issue with the iPhone, it’s an issue with the 20W adapter and BE SURE it is plugged into a wall outlet, not to an extension cord.
As simple as it may sound, just getting a 20W adapter replaced and changing the charging port directly to a wall outlet, it passes 80% like it isn’t even there.
If you charge it from anything below 20%, because of the heat it will stop at 80% for 5-15 minutes before continuing on.
I did all this with “Optimized charging” switched on, so you shouldn’t have any issue! Hope this helps! 😁🤞