Right now, it seems to have a bug when used in combination with a SuperCIC. As soon as the SuperCIC is enabled in the configuration, there is no picture and sync is lost (also, weird readings on the OSSC display). Upon switching the frequency, the LED of the console turns red and is stuck in that status. According to this thread, a firmware update is needed for one of the SuperCIC chips. I’m looking forward to see if this can be resolved through a SD2SNES firmware update. Otherwise, I’ll have to desolder and flash one of the SuperCIC chips.
When I bought the Mk.II many years ago, it was just a PCB and I had to modify an SNES game case for it. The new Mk.III comes in an Everdrive case. However, it is missing a window/hole for the status LEDs.
Comparison of Mk.II Rev. E1 (upgraded to Rev. H) and Mk.III Rev. B: The major components have been moved from the back to the front.