Welcome to gen 4 ls dod that is super finicky…my best advive is get hptuners and a dod delete kit and convert back to standard cam and no displacement on demand. They save gas in cars but in trucks they are just not worth the hassle. If you are bent on keeping it then yes you need a good scanner and some mechanical oil pressure guages and see if its pressure caused or a faulty dod lifter. If a vustomer supplies me with a gen 4 to swap in their car i wont even install unless we delete the dod system. They are problomatic at best.
Good luck…its a simple system but very finicky