The detail that solves this is that the trigger still feels normal. That tells us the mechanism is travelling its full distance, so the problem is the sensor's relationship to that travel, not the travel itself.
An analog trigger works by rotating a small potentiometer as you squeeze. The sensor has a fixed electrical range, and the trigger's arm is meant to sweep it from one end to the other across the full pull. If that arm slips on its shaft, or the gear that drives it skips a tooth, the trigger keeps moving the same physical distance but only sweeps part of the sensor's range. The reading then starts at zero, climbs normally, and stops early, which is exactly your 0.52 ceiling. A failing sensor looks different: you get noise, dead spots partway through the pull, or a value that jumps around rather than a clean stop at a consistent number. A consistent ceiling is positional.
There is also a software possibility worth eliminating first, because it costs nothing. If any remapping tool, vendor utility or Steam Input configuration has a trigger output range or sensitivity curve applied, you can get a clipped ceiling with perfectly healthy hardware. Close all of that and retest in a clean browser session before you open anything.
If it is hardware, the repair is reseating the trigger's potentiometer arm so it engages across the full range. No soldering. The part sits in the trigger assembly on the shoulder of the controller. If the arm or gear teeth are visibly damaged rather than just slipped, the whole trigger assembly is an inexpensive replacement part and dropping in a new one is easier than repairing teeth.
And a word on the workaround you will find elsewhere: do not fix this by raising in-game trigger sensitivity so half travel counts as full. You lose all your fine control over braking and throttle, which is the thing you noticed was wrong in the first place.
