Steps to reproduce on the master branch:
- Load the save from this post (https://forum.simutrans.com/index.php?msg=202114)
- Build 3 tiles of railway track
- Build 3 tiles of road to create a crossing
- Build 3 tiles of tram crack along the road
- Remove all ways
- Notice that monthly maintenance is now not equal to 0
Thank you for your report. I believe that I have now fixed this; I should be grateful if you could re-test in the next nightly build.