Broken down, help, urgent

[renault12ts]

The relay you removed could have a dry joint. If you have a soldering iron you could try remaking the solder joints.

 

[E55BOF]

I'd clear all historic codes then go from here.

If you have not yet done so, do it. (What code reader are you using, by the way. I ask because my [genuine] iCarsoft MB II won't always clear fault codes in 'Benz' mode, but will do so in 'OBD' mode. I've no idea why, but it works...). Forgive me if I'm teaching Granny to suck eggs, but the thing with 'historic' codes is that they become historic as soon as the car runs again and whatever was causing them stops doing so.

Clear all the codes you can, replace the brake light switch, check if there are any uncleared codes, and keep the code reader in the car. Fingers crossed the problem does not recur, but if it does, read and record any new codes before trying to restart the car.