We have had a little instability with MR52 and CW9166 models, bit don't have any MR46.
I do have an MR55 at home on a 100ft cable run that is a mix of Cat5 and cat6 and that is stable into an MS220-8p while drawing 10.4W
What AP firmware are you running and is there a correlation between the devices with cables over a certain length (e.g. 100ft) and the instability?
Have you tried fixing the port speed?
We also have a few Axis IP cameras with 60-70m+ CAT6 cable runs that just don't even power up from MS355s when they work just fine on a Caralyst 3850...