I have some strange behavior at BP.
First of all I play a new game with mods, my game got +20h and it is attached here (Julio2k20).
When I create a new BP it dont take any entity in it, just a empty BP.

I try to load a old save game (just a few mins) and i got this:

I can make a BP that contains 2 train signals and nothing more
Before it i got Dectorio installed and the problemas was that:

I test it with other entities:

Im not sure if the problem is a mod or not, I test in other save that I use the same mods (Creative mode)¨and i get the same result.
PD: The test tool has the same behavior.