In vehicle list, vehicle type trams is not allowed to be filtered.
I have some trams in game. I sent some ones into depot - but I did not know to which depot they went.
I wanted to see (in vehicle list) only trams - but no one was showed.
I used some other (special) filters - but they run only alone or with else vehicle types. In all cases no tram is showed.
Trams are inteally trains for most purposes. This is rather an extension request (and a quite reasonable one).
But they are not showed also in group of trains, too.
This is a bug. The filtering is still broken.
Edit: It seems that the enum flags in convoi_filter_frame_t are limited to 16 bits, and thus break some filter buttons.
Edit2: Fixed with r6066.