Teranex Mini - Incompatible Signal

I have a Teranex Mini which I am feeding a HD SDI signal from a Decklink 4K Extreme 12G. The Teranex Mini then converts the SDI signal to HDMI and feeds into an LG B6 OLED.

Up until a few days ago, this setup worked without issues. But suddenly, without any hardware or software changes, the television no longer recognizes the signal from the Teranex Mini's HDMI port.

Occasionally, when outputting from Resolve or Premiere, there is a very distorted, glitchy, almost analogue-looking image that appears on screen for a frame or two.

I have tried feeding the HDMI signal into a few other displays - some work, and some don't.

I have also found that running the SDI loop output of the Teranex through my BM SDI to HDMI microconverter gives a clean, uninterrupted signal.

The Teranex mini is running the latest firmware, resolve 14/premiere CC18 and i'm running Windows 10.

I read elsewhere that this could be an issue with HDCP, but as the issue happened with no change to software or hardware, this doesn't make too much sense.

Any help would be appreciated!

Thanks!