If you saw all three videos, I believe the 2nd one was after he took the amp to his dealer, they tried the SPAX7 as a few people suggested including myself. I also recommended using a JAN/Phillips or JAN/GE 5751 in V1 to see if that corrects the issue. According to his statements they got the local Mesa rep involved. He claims he does not want to return the amp, just pointing out there may be some settings that get the squeal. Nothing more. His intent was to ask other Reissue owners if their amp will do the same thing. This is only one person's experience and does not reflect the masses. Heck, I have an ice pick Mark V90 I bought in 2012. I should have returned it but opted not to do so, how it is a 65lb pile of trash. (combo amp). CH3 was more usable than it is now, all it does is squeal with no guitar plugged in. It could be just bad preamp tubes. It suddenly died into the squeal mode when trying the amp with the Mesa 410 guitar cab.
With no signal at the input. self driving feedback could be an issue. If that is the nature of the beast, so be it. That is the same reason why I do not use the shred mode on the JP2C as that does the same thing unless I am playing at bedroom level.