Problem 1: Inconsistent signal placement options.
All of the track segments in the following picture are the same, but with different orientations and being flipped. They all consist of a single straight track, followed by a split containing [5 straight track pieces / 1 curved track piece (left or right) + 1 diagonal track piece].
https://imgur.com/gallery/4N7LYAP
Note that the upwards facing track that curves to either the left or the right (bottom left of pic) and the left/right facing track that curves down (bottom right/top-mid right) all allow a signal to be placed that the other 4 track sections do not allow to be placed.
Problem 2: Inconsistent signal placement in these buggy signal locations.
If the above problem is solved by removing the signal placement locations that were only sometimes allowed, this problem already fixes itself. Otherwise, this is the problem: Note that all signal placements in those buggy locations should connect to the straight track piece, not the curved track piece. Well...
https://imgur.com/gallery/bV0bj6J
Note that most bottom left track segments signal is attached to the straight rail, as it is meant to be, while the other 3 signals that can be placed in that position attach to the curved track piece in an invalid position (I have tested that all 3 are connected to the curved track piece and they all are). These signals that connect to the curved track in invalid locations also do not stop signals from being placed directly next to them, and also act incredibly jank with signals in these locations. It would be easier to test yourself or for to show you via either discord or youtube as placing the signals on the tracks, removing then replacing the tracks, and placing a locomotive in front of the signal in different orders gets many different results. One of the most bizarre examples I have found with only a small bit of testing is this, a light stuck on red with no locomotive in front of it (sequence: Place all tracks, place bugged signal, place locomotive, add normal signal, remove locomotive).
https://imgur.com/gallery/KZUgHiA
The next picture is the same variant of junction, glitch and sequence, showing that this light is used by the locomotives and remains stuck on red (the locomotive here is on automatic, trying to get to the station).
https://imgur.com/gallery/nsFT0eC
https://imgur.com/gallery/HEgPgjo
~ Ralp