Atomic Systems

I am very new to Train Sim but must admit thoroughly enjoying it.
I am now creating some free roam scenarios (by cloning a standard one and then amending) however when I try and couple some class 2 x 422 units together I get a derailment despite coupling at less than 1mph. Any ideas what the issues is? Same applies for other classes so I must be doing something wrong?

Are the handbrakes of the stationary vehicles "ON" before you try and couple up ?

I had a similar issue recently while I was shunting some coal waggons. Zooming in while coupling up, with the handbrake "OFF" the buffers passed through each other without the couplers coupling, then the stationary waggon would jerk backwards with a likely derailment. Turning the handbrake "ON" seemed to cause the automatic coupling to activate as soon as the buffers touched.

Make sure the kuju assets are ticked/enabled in the scenario editor then re-save your scenario. Many models use the default couplers in the kuju asset folder and if you do not have the kuju assets enabled for the scenario then I am pretty sure you get the derailments when you try to couple. Not sure if the 422 uses couplers from the kuju assets or its own, but worth a try? Another thing to try is to move the trains and try coupling up on a different bit of track. Welcome to the simulator - it can be tricky to get used to all the nuances of the TS2014 at first but you will soon get used to it in a few months and you'll get plenty of help on this forum if you get stuck so you keep enjoying TS2014