Also, the train connections worked out. Just on the way back, I made the error to use the toilet in the train. I've experienced way worse, but there was certainly a little Urine odor in the air. Second thing I noted was a large pile of toilet paper in the bowl.
When I wanted to wash my hands, I got the soap dispenser to work, but the tap just dripped extremely slowly. Not usable. Then it clicked why there was all this paper in the loo. I tried to wipe the soap off with toilet paper as best as I could and then used my water bottle to rinse my hands. Luckily, I had topped it off before I left the office. I only had to use my jumper to increase grip for actually getting the lid off. The sparkling water happily soaked my jumper and the floor in an instant. :-D
Tip for your next train ride: Bring your own water supply, preferably non-carbonated. Alternatively, just use the office toilet beforehand.
Turns out that at least this train model has two separate water tanks. One for the faucet and another for the loo. I flushed the paper without issues before I left.