The road vehicles do not cause a problem as they swap to the opposite, (correct) side of of the road and continue in the appropriate direction when this occurs.

The trains cause a major problem as they stay on the same track when they reverse.  They then try to proceed in the opposite direction on the wrong (LH) track, instead of the correct (RH) track.  This causes gridlock in you fail to notice, and correct the problem immediately!  Often this only becomes apparent when a previously profitable line starts to make a huge loss!

This is a major bug in the game and need an urgent rectification!  Can we have some urgent action from the devs please?

The solution is obvious, and would even make the game less resource hungry: Run the pathfinder only on demand. It is appropriate that it runs when you make a new route. When you change either the route or the track/road, it should give you a hint that you need to take action, but it should not start on its own. Only the player knows when a change is finished and ready to be committed.