I use a Jobo Expert 3006 drum with PMK and have had every problem there is with presoaking. I think PMK is sensitive to this. Now I have a method that works well. I insert the film into the drum that is flooded with water. Lid on and top of drum with water and then displace the water with dry nitrogen gas and put in a cork. Onto the base and add the B part with half the total volume of water, i.e. I use 1000cc of water, so I add the B part to 500cc of water. This runs on the base for 2 minutes and then I add the A part with its 500cc of water and start the clock. The nitrogen is just to reduce oxidation that affects staining with PMK.
With another technique, I don't presoak. For scenes that need extreme compensation with good low end development, I put the film into the drum dry. On the base, I add about 500cc of PURE A STOCK for a few minutes. The film soaks up the A stock, but no development takes place without the B stock. I then remove the A stock (save this back into the bottle, it is fine), and put in the B stock diluted, i.e 20cc B to 980cc water, and start the clock. Works great. No nitrogen gas needed for this type of development.