Brake Light Error: Handbrake Warning Light

Hello dear colleagues,
I'm having a problem with the handbrake warning light on my Passat TDI 1.9 4Motion.
After driving approximately 30-50 kilometers, the warning light illuminates (indicating the parking brake is engaged).
The handbrake switch and brake fluid reservoir have already been replaced. WHAT ELSE COULD IT BE?? HELP PLEASE.

Can I check the error memory at the exact moment the light turns on?
What do the brake pads look like?

The brakes were completely replaced about 5,000 km ago, and the problem only occurs while driving, not when the car is stationary.
I was thinking about doing a test while driving to see if there might be a problem with one of the ABS sensors. ???

Glöckner Guido wrote:

Brake fluid reservoir has already been replaced, PLEASE

.

Warum wurde der getauscht? Auch der Geber? Ist genug Flüssigkeit drin und bleibt sie auch drin? On Max?

Could something be obstructing the handbrake lever from being fully depressed?

The container was replaced with caution and under suspicion of a potential issue related to a Volkswagen master technician.
The customer is now with me, and I'm trying to resolve the issue.
"Handbrake helper" is obviously a typo; I've already corrected that small error.
I think it might be related to the ABS/ESP system or a circuit board.