Four things to try, if this is happening with with different locos as you suggest. Give the track a good clean .invest in a good track rubber.Check your rail joiners are secure.Is your layout fed with just one connection. Try a multiple wiring ( bus ).Points. If you use point clips check these are secure.Have you had a controller failure? I would not have thought a DC runaway would damage a controller, another track issue?, intermittent point fault / stray track pin?