After two years of riding, I finally gave up. For the first two or three months, I heard clicking/squeaking noises. I thought it was the bottom bracket, maybe the Ninja-Token bearings, maybe the wheels – lots of different ideas. But it was the left arm of a Magene P505 Base. After reassembling it, it helped for 200-300 km, then the noise reappeared. I ordered a new bolt, but that didn't solve the problem.

I like the look of the P505 Base, and the accuracy is quite good, but the noises coming from inside it finally got annoying, and I gave up. I put it on my indoor trainer and am looking for a new power meter for my outdoor bike.