D455 Malfunctioning - Registers Depth of Millions of Metres

I am using the D455 sensor.

For several weeks, the sensor worked normally without any issues. Then, a few weeks ago, I activated the Stereo Module and it started registering depths of either 0 metres or 1 million+ metres (the camera is in an office setting, directed at a wall ~3m away). The issue remains no matter what preset (default, custom, etc) I use. When I activate the Motion Module, I get the error "Motion Module Failure". The RGB camera works normally. Other Intel RealSense sensors (L515 and T265) work normally. 

Even stranger, I don't get the same errors every time I connect the camera. Once I received "Right MIPI error", another time "A device attached to the system is not functioning", and sometimes there are no reported errors at all - just the bizzare depth values. 

The camera is usually used indoors, and was used outdoors once for several minutes under dry, sunny conditions, where it operated normally. When not in use, it is stored in its original packaging on a shelf in an office. It has no external signs of damage, nor has it experienced any potentially damaging events. 

I have tried (without success):

• disconnecting and reconnecting the sensor
• turning my computer on and off
• relaunching AND reinstalling the Intel RealSense Viewer*
• updating firmware
• performing a hardware reset
• performing a factory reset using the tool CustomRW
• leaving it alone for 2 weeks, then retrying

Can anyone help me figure out what is going on?

I know this is a long post. I wanted to provide as much useful information as possible and I thank you for your patience!

*I am using v2.50.0 of the Intel RealSense Viewer, which I know is not the most up-to-date, but it is the latest version that supports all three sensors that I am using. Using this version never caused issues up to this point.

Cheers