I'm experiencing the same problems described in Having a problem with an AWR model for AFT05MP075N, but using both MRF1K50H & MRFE6VP61K25H AWR MWO non-linear models. This happens on HB simulations, linear & DC work fine. I'm using AWR 14 and correctly installed the latest version of the High Power Model kit v.11(other transistor models, such as MRF300AN, work 100% correctly also on HB).
Thank you in advance for any help you are able to provide.
Update: the same thing happens also with MRFX1K80H. Strangely enough, in this case I was actually able to perform some HB simulations, including a Load Pull analysis. When I attempted to change the schematic frequencies, the error appeared again. From then on, no further HB simulations were possible.