Try one of the old heavy wall wart power supply rather than the new lightweight switching mode models. I'm not SURE this will make a difference but I haven't had problems with my Thermoworks probes... 12VDC is a very common power supply, so I bet you have one around.... Cordless phone, old answering machine etc....
My Maverick 732's are totally unreliable without the braid grounded, so I use them as a second probe and use a clip to connect the braid to a Maverick 73 probe braid (which is grounded) and then they are fine...
Maverick 73 High Heat probes had been my favorite, cause they didn't have ground issue and they can stand over 700F, but they are not particularly resistant to water, I've soaked out and burned up a few of them for sure... I generally use a 73 as a pit probe and the 732 or Thermoworks as food probes, but am looking forward to moving to a thermocouple for the pit probe pretty soon here....
You could take a 2.5mm plug and wire an alligator clip to the ground and plug that into an unused probe jack then clip it onto the braid of the flaky probe... I know, not ideal, but it would work... Or alligator clip jumper wire from the probe braid the the rPi LAN housing, it sticks out enough to clip too...
I know Bryan has been working hard at eliminating noise on the probe lines so perhaps the next HM board release will be more forgiving of these grounding issues...