Eclipse Version: 2018-09 (4.9.0)
Eclipse Build id: 20180917-1800
Enhanced Class Decompiler (Core) Version: 3.1.0.201807021924
When leaving a tab with a decompiled class file (as in choosing another, not closing it) the line numbers have disappeared when the tab is accessed (re-entered) again.
When switching them on and off again, they will reappear.