Mixing Refrigerant on a Rack a problem?...How say you?

It really depends on a couple of things. First, the makeup of the two gases, how similiar or different are they, and also the percentages. We all know jobs that run small critical charge, and others that are hundres or thousands of pounds. Peeing into an ocean doesnt make it polluted, but peeing into a twenty ounce glass clouds the water severely.
In this case, it appears you are ok, or at least close enough to keep 'em running well. At some point in time, you may experience problems.

All my customers have humming bird size units compared to you guys. I don't even consider mixing gases. Once the mineral oil is finally gone and POE oil takes over it should eliminate one head ache.