Plaits drifting frequency

I bought a Plaits today. I installed it in my case 4ms pod60 and it worked perfectly.
After half an hour it started losing pitch occasionally (drifting through semitones) and eventually it started glitching consistently.
I thought it was a calibration problem but I have re-calibrated it correctly (I think) and it keeps drifting.

here’s how it sounds:

Things I’ve already checked:

  • im not in LFO mode
  • every other patch cable is unplugged
  • calibration should be fine

other information:

  • the case doesn’t have the original power supply but the specifications are the same
  • in the case there’s only Maths and Plaits
  • Maths is not giving me any problem