J.S., I had the same problems that you were having at first. I was able to mitigate these problems by
1) never using less than 2 liters of working solution
2) shuffling from the side, not the top.
3) I put the film on the top of the solution, than pat it down in the middle
How has your experience been with PL100 using straight abc? Do you get the contrast you would like? What do you rate it at?