There are two main reasons for locos stopping: (1) A short, and (2) a loss of power to the loco.
There are two indicators to look at: (1) the LED on the power supply, and (2) the hand-held controller (HC). I don't recall exactly what message the HC gives, but it involves a red indicator on the screen. (My layout is down right now for a rebuild of my control panel.)
When the loco stops, the HC indicator will always be red. If the power supply LED is also red, then you have a short. If the power supply LED stays green, then you have a loss of power to the loco.
The most common reasons for a loss of power are (a) dirty track, (b) dirty pick-up wheels, (c) uneven track, causing a some pick-up wheels to lift off of the rail temporarily. All of these are more common at turnouts because when one of the pick-up wheels goes over the plastic frog, you are temporarily relying on fewer pick-up wheels.
The most common reason for a short is that the loco wheels are momentarily touching BOTH rails at the frog. The fastest way to diagnose if this is is the problem is to temporarily put a small piece of tape on the rail at the frog that the loco is NOT supposed to touch.