Scripted signals remaining dark



Does anyone have scripted signals that remain dark?
I have a route+session with build 5.0 that works in TRS22. But I need to make changes unrelated to the problem presented here.
I go to Edit Session, do not change anything, and Save As (new route + session). Once I go to the session saved from within TRS22 (122411, build 5.3) the problems begin.
Once in the build 5.3 version, I find that many signals are not lit, and the semaphore arms do not move. This holds for both editing and running the session.
(In the route that I saved as build 5.3, the signals are properly lit. But, I need to work from the session, which contains schedules for about 20 trains.)
I also just found that it is possible to "Unpause", even in editing mode. But that does not solve the problem.
In editing mode, there is a new pop-up screen for the Properties button of the Trackside menu at right (the "?" button in the menu).
For properly working signals, the pop-up screen shows the signal state, the colour, and the link to the relevant junction(s). The latter is found by clicking the "triangle" behind "Signal Reason" on the pop-up.
The dark signals, however, only give a signal state. The colour is "0" and there is no "reason" and no link to a junction. (In one case I found an entirely incorrect link to a track marker in another part of the route...).

I found that removing the dark signal and replacing it with the very same asset, does bring the signal to life.
But for the whole route, that would be a lot of work...

Somehow, during startup, the signal does not find the path to the junction that it guards. So far, I have not found dark ones among the caution signals that are followed by a stop signal further down the line.
The signals are of my own making and use an extended version of the script by bloodnok.

Thanks for any suggestions.