Streaming stops when camera is in low light/dark

[alandpearson]

Hi , first time using openIPC, on a hi3518ev200 board.
Got it flashed and mostly working.
The issue I'm facing is when the camera is in low light conditions, streaming essentially stops until the light level is raised again (I can see the OSD freeze when the camera goes dark, then start again when light is restored.)
What is odd is that the preview mode in the WebUI shows the camera operating as normal, it is only streaming (via RTSP) that appears to freeze.

Any ideas what could be going on ?

Thanks for any help.