Never have been able to get soft points to feed, in ANY large AR...
I'm convinced they are designed around feeding FMJ and OTM type bullets, and anything else they'll feed is icing on the cake......
Randomness such as you describe, suggests a loose or non-spec barrel nut torque, IMHO. That may also not be the case, but it's a decent starting point.
LOL...
I might be mistaken but I thought you told us once that your DI said you could break an anvil with a rubber mallet.... I'm sure it's true in any case!