Strangely enough, it's only there and none of the other externs!

Then, about three weeks ago, I found moisture and running traces in the water catcher box at the heating lock valve and the nozzle with the fan screw. I repositioned the hose clamps and it has remained dry until today.
Yesterday in the afternoon I took a 200km exit. Today I have renewed the air and pollen filter and noticed that a little more than 1/4 liters of cooling water is missing.
The water box is still dry.
So far, I've checked all the suspects, and that's:
- Water gallery
- Water pump
- Balancing tank and hose connection
==References== Illuminated below
- gr. Radiator hoses
- Carpets are dry
Why do I have water loss and why does it only smell from the left airflow, but can't find anything striking anywhere?
I don't have any stains under the vehicle.
The heat exchanger (Hella-Behr) was only exchanged 2 1/2 years ago.
It's very puzzling. Tomorrow, I'll pull the trigger. Unfortunately, I still do not know where the water is when the result is negative.
Do you have a plausible idea?
Greeting Andreas
