FOSS gamedev and creative worlds

Hi!
I logged in today to my minetest server on Debian Jessie. I changed neither the game, not the mod set.
But now, all logged in players are unable to move. The players move arms and legs, but don't change
their position. Also jumping is not possible. Created a single player game, everything works as it should.
I don't want to lose my world as I played so many hours. Nothing to see in the server logs.
What can I do?

After saving the current world and creating a new one, i also could not move.
The problem is one of the last commits of the 3d armor mod.