I have had that problem.
The fix for me was to change my process to keep the solutions from getting contaminated.
I'm using a JOBO and reliably get 20 8x10s using 200ml.
The last ten seconds of each bath is draining.
Pre-rinse twice, 30" each clean water
Develop for time appropriate for the temp in use
Stop bath 30"
Rinse, clean water, 30"
Blix for the same time the developer got
Three 30" rinses in clean water