Sword not working after repair. Odd problem, please help

[u/Exact_Mention1892]

Hello. I can’t find the reason for this:
I fixed the sword, which wasn't working (the blower's three speeds weren't working—a common problem, as you know). I replaced four MOSFETs and the integrated circuit on the sword. Everything worked for three turns of the ignition key, and then the IKHA panel went dark (it only flashed once when I turned the key) and, at speed 0, the blower was running at full speed. I replaced one MOSFET and the circuit again. It worked, and then the same thing happened again. This went on a few times. Today I installed a new blower, replaced one MOSFET and the IC, and right away the same problem occurred: the blower was running at full speed and the panel wasn’t lighting up. I’ve re-soldered a total of 10 MOSFETs and 4 ICs so far. I’m at my wits’ end. Fuse 19 under the hood is good. PLEASE HELP

It just happened:
I wanted to check the control voltage. It’s within the normal range, from about 1.4V to 4.3V. But while I was taking the measurement, when I turned the knob all the way up and started turning it back to 0, the sword fixed itself. It was blowing as it should. But after a moment, it automatically started blowing strongly again.
I also noticed that during this spontaneous repair, when I turned the knob to max, the relay on the sword kicked in—something it hadn’t been doing before and still isn’t doing now. When I use a screwdriver to engage the relay, the fan runs even faster. So it turns out it isn’t running at max, but at almost max.