LED flashing error code

[Hans]

I bought an "in-house built" V1.0 OneRNG (plus programmer and cable) as part of the Kickstarter, and it has worked well for quite a while. Several months back the LED started blinking. I thought initially it was "random", and only recently got a chance to look closer. It seems to be flashing the 1 second on, 3 seconds off code, which from looking at the source code apparently means the avalanche noise source is stuck at zero.

Is this a known failure mode for these vintage units? Could it be something obvious or easy? I'm capable of SMD work. The scope is dead or I would have quickly looked at the noise input to the CC2531.

-hans