When left-clicking on the reactor's control interface panel (to open the GUI), it throws a non-recoverable error and kicks the player back to the main menu.

The error:

1441.051 Error MainLoop.cpp:1281: Exception at tick 93696: The mod RealisticReactors (2.19.0) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event RealisticReactors::on_gui_opened (ID 84)
Unknown style icon_button
stack traceback:
[C]: in function 'add'
RealisticReactors/scripts/stats.lua:743: in function 'create_signals'
RealisticReactors/scripts/stats.lua:592: in function 'create_gui'
RealisticReactors/scripts/stats.lua:437: in function <RealisticReactors/scripts/stats.lua:419>

This happens consistently and with both reactors. Was found in a heavy modded environment but then replicated with only Realistic Reactors (and Base) enabled. The mod seems to work fine otherwise.

Mod version: 2.19.0
Game version: 1.1.6 build 57355 linux64
OS: Manjaro Linux 20.2 64bit

Fixed in version 2.19.1. The error was caused by the start/stop button in the GUI.

Unfortunatly I couldn't find out what causes this error, so I had to disable the button. This means you have to use signals to start and stop the reactor.

Thanks Ingo, that was a really fast fix and I didn't expect you to get it done right on the holidays. The button isn't a huge loss, personally at least I always used the GUI just to keep an eye on temperature and cooling.

Happy holidays!