Positive to the line overview which erroneously includes rail line in the road vehicle only filter.
Don’t know if the issue about unable to set the train to line due to grouped station has been fixed. Since the line overview bug hasn’t been fixed yet, I assume this is still the case. My guess is that you accidentally clicked the bus stop/terminal while creating train line, this function is supposed to allow you to select a specific side in a bus/tram stops group when they’re grouped together automatically because you lay the second stop right on the opposite side of the road. If you don’t select a specific stop, the program automatically designate either stop for the line.