I'm a Newbie with all this wizardry, having just made the leap to DCS in the past couple months. I've had several experiences with that exact scenario, but can attribute it to loss of wifi signal. I used to use my phone, but every time someone called or sent a text, it would screw up my MTH dashboard. Had a few close calls with that.
I have also had total loss of control of running trains, again, due to loss of wifi (in my opinion). The only cure was shut down the transformer (quickly!!!), close the app, and re-open it. When I reopened the app, it saw the engines, but in the process, the app would lose settings like speed restrictions.
Now, I only use my iPad because no one can text to it. I have a hand-held on order that I look forward to getting. I have also had the loco stop and the horn blow, but by far the most annoying thing I experience of the random firing of couplers. Still researching that.
Another conundrum with my iPad is it is also an independent mobile hot-spot. I would expect the WIU to see it, since it's "always on" just like any other wifi, but the MTH wiu doesn't see it. so I just run everything runs on the house wifi.
Good luck. Hope this helps!