Just bought one of the newest batch, and seeing the same problem, good image from the Eyesy over composite when direct into a TV, monochrome and glitchy when through two different Panasonic mixers. an MX-10 and a WJ-AVE55.
Everything is PAL, no problems from the mixer with any other composite-out devices that I can find.
However Ive done some testing with two Pi3 boards, one running MP4Museum v6, the other running R_E_C_U_R, and the same thing happens. So I guess its intrinsic to the RPi composite out.
Cheap and cheerful solution that works straight away is just fire HDMI through a £6 HDMI2AV box from Amazon, though I may look into a couple of other options.
A bit annoying, though, in that I got the Panasonics because they were supposed to not lose sync with odd and/or glitchy video signals.