Annealing is a good idea for the neck and shoulder,
maybe try graphite powder or a smidge of Imperial Sizing Wax if the lube is contributing to dents in neck/shoulder area.
But can't anneal much below shoulder,
and you may have the harder and springier lower case wanting to spring back as it comes out of the die.
Ouch.
Size one repeatedly and see if you can get it to chamber, being sure it is trimmed.
The cases may be growing in length enough with the diameters reductions to interfere with chambering.
But you did say you trimmed to max length of 2.850", eh ?
Maybe try trim-to-length of 2.840" then let cases sit overnight to see if they slowly grow in length or diameter after that prep.
Sometimes a re-sized jacketed bullet does.
