When you mine the bridge while it is open to let a ship pass, 3 "bridge_crossing" entities are left behind which cannot be removed. Those entities also prevent you from placing a bridge at the same position again.

thanks for the report, i will look into it

I have to add that every time I checked this, the ship (that the bridge was open for) was right beneath the bridge, so probably that's the problem.

while i havent looked into it (and also it might be some time til i get the chance) that is what i allready assumed was happening. a train track cant be destroyed if something is ontop, so i will have to make the bridge unminable, as long as ships or trains are "ontop". but thanks for the clarification!

this has been fixed in the latest release