2013 BRZ Evap self test knocking ticking clicking
 

After normal driving, 2013 MY BRZ runs a fuel evap leak test approximately 5 hours after shutting the engine off. It's common to hear a soft humming/buzzing noise from the rear of the vehicle under these conditions.

Recently my vehicle has been spicing it up with some percussion. Just wondering if anyone could identify a clear problem from sound alone.

Useful notes:
- Just under 100k miles
- No power/drive train modifications except for Perrin catback exhaust
- Only notice these noises towards the end of the test (video below captures a few seconds after the noises started, but I had been listening for a few minutes before recording)
- No issues filling up
- No noticeable fuel vapor leak in my garage or otherwise
- No CEL/MIL
- No codes when scanning (besides solar circuit due to low light) - I have been trying to catch codes for this sound for a while but it doesn't seem to be tripping any malfunction indicators
- Engine seems to be running just fine

All of the above tells me it's probably just a noisy solenoid somewhere in the evap system. Not too sure about the groaning noise though... Anyway, if anyone has an idea of what's going on I'd appreciate your insights.

https://youtu.be/AYwT7UqVKiQ