7i97t Mesaflash Problem

Furthermore, the Mesa disconnects after approximately 5 minutes with these values. The 1A Ff fuse doesn't blow, but the wire deforms. I suspect that due to increased contact resistance, the voltage at the Mesa is no longer sufficient.

Yes, the PWM value (from the PID component) should increase as the position
error increases.

Did you check the 5V power?

Are CR23 and CR27 (Yellow LEDs near the center of the card) both fully illuminated?
(these LEDS indicate the analog +16/-12V power supply operation)

The lower LED is slightly dim. I adjusted the voltage; it was 4.6V, now it's 5.1V. When I move the axis, the fuse trips immediately, but the wire only deforms slightly more. Is 1A too low, or is the Mesa fuse defective?

I would venture a guess at wrong wiring, so first check if analog grounds are wired correctly, from your explanation this seems to be the reason.

I haven't wired them up yet, but the fuse issue also happened when the power amplifiers were connected.

What Mesa fuse? There are PTCs to protect the 5V encoder wiring, if these trip, you have a wiring error.

I installed a 1A FF miniature fuse for the Mesa.

If a 1A fuse blows with no encoders connected and analog outputs open (or at least not shorted).
the 7I97T is damaged...