Error 16955/17978: Causes and Solutions

Hello, after trying to search and unfortunately not quite understanding the context, here's the process:
The preheating spiral on the Sharan AHU is illuminated, and I'm reading a single error code: 16955, which indicates a problem with the brake light switch.
After the error was cleared, the problem reappeared: the brake lights are not working.
"Bought a switch, now I'm getting two error codes: 16955 and 17978. The motor is locked!"
Heart slipped into pocket ''

After installation: all errors cleared!
Started with the brake pedal pressed - stalled. Restarted without the brake pedal - it runs.
Engine control unit fault... it's back again.
Errors fixed and clean.
I haven't done anything else related to the immobilizer or the key.
I know that the switch also cuts off power during braking, and that it has two opposing switches. But I'm wondering why the main control unit is being blocked.
If it's supposed to be normal, why weren't both errors present at the same time?
Please explain to me why.
Thank you in advance.

Quote:

Started with the brake pedal depressed - stalled.

When he left, he probably experienced occasional instances where the key was not recognized.

For example, in older Polo 6N models, the problem is often due to the connectors, which cause the signal to be too weak.

What does the fault memory of the WFS (Vehicle Information and Entertainment System) or the instrument cluster say?

Hi, it's a Sharan, not a Polo, but whatever.
I checked for all errors, not specifically WFS errors, but all errors were found.
However, it's not yet being done with VAG-COM, as that functionality isn't working yet; instead, it's being done with Techmess.

Okay, so I understand correctly - there's no connection to the BL switch story?

Quote:

Hello, Sharan not Polo but it doesn't matter,

It was just meant as an example.

Quote:

So, am I understanding correctly - there is no connection to the BL switch story?

Normally, no.

Ah-yes, thank you.
Okay, I'll check back on the FSP again sometime to see if the WFS error reappears.
I also have to delve into the VAG-COM software to find the WFS.
At Techmess, the address is simply the engine control unit or WFS/ABS, etc.

Thank you again.