154.107 Error MainLoop.cpp:1510: Exception at tick 13148400: The mod Signal Display (1.5.1) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event signal-display::on_nth_tick(30)
LuaEntity API call when LuaEntity was invalid.
stack traceback:
[C]: in function 'index'
__signal-display/scripts/events.lua:33: in function <signal-display/scripts/events.lua:9>

Thanks for the report.
Can you give any further context?

Other mods active, what you were doing?
Any surfaces recently created, deleted?