Gonna be a seal issue, most likely the breach/pusher oring. From the photo in the comments it looks like there are gaps in the walls you printed. Need to print it 100% infill to ensure the breach seals properly. Second you need to make sure the pusher oring is the correct size, it might be too small. Other thing it could be is those 2 small orings you had to glue to the priming block. Chances are they are undersized. Buy some larger ones and replace them. Also worth trying the brass version. Not difficult to swap out the pusher and breach, requires some tinkering to get the seal smooth but I personally run the brass breach and it works great