Bein part Scot myself, I can understand your concern, but it might do more harm than good. Film blixes are on the very ragged edge of being able to blix properly anyway and I don't recommend them. So, to beat the problem as best you can, fix the film first in a good neutral pH non hardening fixer. Use about 6 minutes at 100 F, then wash 6 minutes at 100 F and then use the blix for twice the time, but diluted with more of the neutral, non-hardening fixer, not with water.
That "might" work. IDK. Better than nothing.