I do my chicken stock the same way.
When the pc gets "to pressure" give it half an hour or so.
Turn stove down to minimum to keep at pressure level - not blowing lots steam.
3 chicken frames (smashed flat with big chopper) come out as jelly with meat falling off bone with finger.
Before starting cook; trim parsons nose and all easy to cut fat from bum (not yours)
This helps, with lower boiling to stop deposits on rubber seal which glue lid and saucepan together.
