A memory leak happens when starting minetest under some
circumstances. it can be fixed by resetting the advtrains save file a
couple of hours back.
A sample advtrains savefile set can be found at:
https://minetest.bananach.space/2020-05-01.17.tar.gz
Btw, this issue does not happen with the new_lzb branch, but as #151
shows, new_lzb has its own share of issues