Erratic behavior with signs and lines view

[abmpicoli2]

Hi.

First of all, great mod! I can see this is a long standing work of love: congratulations! :)

That said, I'm having a long lasting issue with signs in this mod. I did try release 43 and now I'm using beta SVN revision 11633

Adding a sign (alt-s) to a tile is not persisted: the sign vanishes shortly after a save: not even a reload of the game is needed, the sign disappears without warning.

This is not intended behavior, is it?