When I had a stubborn mold, I'd use some green abrasive pad folled to be just a bit larger than the cavity and rotae it by hand or whatever to knock out burrs that might be there.

Trying to remember what the pad is called.............it is like nylon or plastic, so don't do it if the mold is hot.  easy and might work.

Scotch brite.......  it came to mind.

I'd bet your mold is getting too hot.... Every durn time my bullets stick I'm too hot.

Clean it and see, if that don't work try slowing your rythym a bit.

John

I have a PJ .45 mould that does that sometimes.  What happens in my case is the mould and alloy get a little too hot and the cavity fills with a tiny amount extruding into the vent lines and along the border of the cavity on one or both of the blocks.  It takes an extra whack or two (not as many as yours, but it is a heavier bullet) to get the casting out, and it shows a line of tiny little tears along the mould line.  The flashing sticks to the lead along the line, maintaining itself and continuing the sticking (and the tearing) through the casting session.

I have a scrap piece of sheet copper snipped into a triangle, and if the flashing is localized I can get rid of it by rubbing one of the points of the triangle against it.  If it's too extensive, though, the only fix I've found is to take one of those bullets, wipe it with Clover 320, and rotate it five turns or so in the cavity.

To keep it from coming back, I take a Q-Tip with a tiny drop of Bull Plate Lube and go over the block faces up to (but not into) the cavity.  Properly applied, the stuff will not migrate where it doesn't belong, and just a trace of it repels lead like car wax does water.  I put it on the tops of blocks and the bottoms of sprue plates for the same reason.

Whatever finish Mr. Jones put on those moulds sheds lead like magic and the castings will practically fall out by themselves, but it appears that much use and oxidation, and the practice of casting extremely "runny" alloys like Linotype-wheelwright mixtures, seems to reduce this quality.  That's another thing I don't do any more; I use the Jones mould for only lead-tin mixtures.  The bullets come out with a tap or two now.

I agree with Fred's, statement bullet cavity may not be centered. Its easy to check with a Vernier simply measure the depth of each side of the mould blocks at the base. If they are not equal the bullet will indeed stick to the deeper side as it would wrap around the bullet beyond the center line and grip it in place. Hopefully that is not the issue as there is no way to correct it and it only takes being off a few thousandths from center to create that particular issue.

JLouis

John, I just did as you said and measured the blocks. They are fine. Each half measured .450". The two half's  put together measure 1.309". The cavity is .409". Paul was  a tool grinder by trade. I don't think he made many mistakes when it came to his molds. They are a work of art. No this mold went from being really good to the current problem. Hopefully it's the temperature that is the problem and not the mold.

Take care
Bob

You didn't mention what alloy you are using. Harder alloys, especially Lyman #2 or others with antimony on board, shrink very little and can be clingy. 
Smoke the mold with a wooden match.  Wood match, let the initial flare die out, then smoke the mold till it's sooty, like you smoked it with an a rich-burning acetylene torch or carbide lamp.  Or use a release agent.  There's a reason why it bears that name.(    )

When I cast at 800* or a little over I have to give the bullet a little time to cool and shrink. I may go to 30 seconds before I cut the sprue after the sprue freezes and open the mould.
Is the sprue cutting clean or tearing?