Let's try loading with the absolute minimum mods that your save needs to be functional. Disable everything but these:
Unlimited Oil And Ore
Unlimited Soil
Unlock All
Loading Screen Mod
Network Extensions 2
81 Tiles
Electric Roads Mod 2.1
Realistic Population Revisited 1.4.3
TM:PE 11.5.0 LABS
Remove Need For Pipes
Do NOT save, or if you do at least save as a new file! This is just to test if things behave like they should and if the transport lines still trigger the issue. If not, then we're looking for a mod doing something it shouldn't.
Unlimited Oil And Ore
Unlimited Soil
Unlock All
Loading Screen Mod
Network Extensions 2
81 Tiles
Electric Roads Mod 2.1
Realistic Population Revisited 1.4.3
TM:PE 11.5.0 LABS
Remove Need For Pipes
Do NOT save, or if you do at least save as a new file! This is just to test if things behave like they should and if the transport lines still trigger the issue. If not, then we're looking for a mod doing something it shouldn't.