Hey!
Got this error when going to Gleba for the first time with a space ship that had Signal displays that was using your mod. When dropping down to the planet for the first time, it happened.

The mod Signal Display (1.5.0) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event signal-display::on_nth_tick(2)
invalid key to 'next'
stack traceback:
[C]: in function 'next'
signal-display/scripts/events.lua:28: in function <signal-display/scripts/events.lua:9>

Thanks for the report.
I believe I know what the problem is.
Is the bug crash repeatable?
It could be a race condition in the code, I’ll see if I can handle it

When the game crashed, i loaded up the save again, and it happened again. So i would say so :) Thanks for taking a look at it. I love the mod!

After looking at it I believe it was due to an incomplete fix to a previous bug report and appears when the game reuses a surface index.
Can I hazard a guess that the save you are using previously had a ship destroyed?

Hopefully fixed in release v1.5.1