Electromagnetic clock issue with pendulum amplitude

Hello printed clocks lovers,

I had the clock running for some weeks without any issues, when it startet to do double ticks. I then sat down with it again and made some changes with the pawls and thought, that seems to be a lot better than before, but a few days later, when the time was way off, I realized that the pendulum amplitude was not consistently the same (as it was in the beginning). It did not only do double ticks, it also missed even more ticks. I tried with batterie change but nothing changed, I took a close look at the electronics board, but I'm no expert and could see or measure any problem, I just thought, it must be something with the timing, and since I didn't find a way to test/measure it, I ordered a new quartz clock mechanic (they changed the electronics board a bit, but the size is the same, I only he'd to cut away some very tini pieced of the plastic covering the coil to fit it through the hole). Anyhow, also with the new electronics - the exact same issue. It cannot be the electronics then, and before it start to take it apart not knowing where to start to look for the problem, I thought I'll ask for assistance, maybe someone could give me a hint on where to start debugging. how long for example should the pendulum swing before it stops? I was so certain that it was the electronics, but now everything else is under suspicion.

Thank you very much in advance!

Kind regards,

Daniel