This mosfet thing seems to be a false rumor that just won't go away; I dunno how many times others have claimed that all mosfet's do this. I believe these complaints must be setup-related, which in no way differs from any other improperly-setup system of any topology.
In fact I've favored mosfet's with my speakers ever since I first auditioned a mosfet Luxman Ultimate series amp about 18 years ago. I tried out some other amps, but kept going back to that mosfet. When that amp eventually failed just a few years ago (parts no longer available) I began auditioning lots of equipment all over again, & eventually settled on an Accuphase product which I didn't even KNOW was mosfet for the first few weeks that I had it (I mistakenly believed that it was bipolar).
I did hear a couple of other mosfet products that did not synergize at all well with my rig; two Belles designs & a Conrad Johnson. These amps all received some nice reviews by others, so it wasn't the fault of the products, just did not synergize well with my particular combination of cabling & speakers.
Your issue I believe is not regarding mosfet's per se, but does relate to component & cabling synergy, which is really no different than any other design.