I own an LG 65C9, a Zidoo UHD2000 (Firmware 2.3.35) directly connected to it and a Denon AVC-X6700H via eARC. I had the same HDMI issues as discussed here when having the Zidoo connected directly to the LG, but not when having it connected via the AVR. Somebody at the forum of android-mediaplayer.de suggested to use an HDMI repeater between the Zidoo's HDMI output and the LG's HDMI input. I followed this recommendation successfully by using an XSource 4k HDMI Repeater. It can easily be plugged in, as it is fed by the HDMI signal itself (no power adaptor needed). It's plug & play, so no configuration or setup to go through. Over at Amazon, 4k HDMI repeaters are traded for 8 to 20 € apiece. I didn't notice a difference in image quality, so I would recommend it to anyone with similar issues.