When powered rails are active I get the following error:

The mod James' Train Mod (2.0.6) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event James-Train-Mod::on_tick (ID 0)
James-Train-Mod/scripts/powered-rails.lua:307: bad argument #1 of 2 to 'pairs' (table expected, got nil)
stack traceback:
[C]: in function 'pairs'
James-Train-Mod/scripts/powered-rails.lua:307: in function 'UpdateTrains'
James-Train-Mod/scripts/powered-rails.lua:349: in function <James-Train-Mod/scripts/powered-rails.lua:346>

Also it seems to have an issue with "solar productivity" mod when powered rails are active

Your save is broken. My mod somehow was not able to set up variables it needs, or they were deleted.

I'm not sure how either would happen.

Loading the save without the mod, saving, then loading with the mod should fix it.