I ordered these same MOSFETs (exact part number) from Mouser a couple weeks ago to finally get around to doing the power supply refresh in my two main Lynxes (a Lynx I, and a Lynx II both with original McWill LCD mods) Both Lynxes are in fine working shape with no issues.
I replaced the zeners with 1N5991Bs and then dropped in the MOSFETs, the Lynx II (first up) seemed to be working fine (quick basic power test) so I moved on to the Lynx I.
While leaving the Lynx I on the bench for extended powered on testing for a bit I thought I smelled something odd. Sure enough the MOSFET was running insanely hot, with a thermocouple MOSFET surface temp was hitting 130C and still climbing. The board was so hot that the heat from the other side of the case seemed like it might melt the rubber button pad.
Going back to do extended power on testing in the Lynx II the MOSFET also seems to be generating the same massive amount of heat, but the board and location is able to sink it immensely better. Surface MOSFET temps were still running away.
Dropping the Lynx I's original MOSFET back in restored normal operation temps. I ordered the Lynx tune up parts from console5 which I think are these MOSFETs and they are installed (in both Lynxes) and working fine at around room temperature.