wiring around mth switches

That's not unusual when adding switches to the mix. The easiest thing to do is add more power drops or lockons. Sometimes the switches (depending on the manufacturer) have power jumpers under the switch and they go bad. Sometimes the track connections between the switches and even between track connections don't make good contact.

Ron

Thanks, Ron!  About the drops or lockons, I think I should do one about every eight to ten feet.  Does that sound about right?  Also, MTH literature states that lockons should be on the side of track where ground is continuous (not on side where switch is insulated for anti-derailing), but with multiple switches that could be on either side of track.  Do grounds on both outer rails create a problem?

As Greg says they won't cause a problem. MTH states that because some people use the common rail on one side other track for tripping accessories and non derail on switches by cutting a piece of the common rail and insulating it from the rest of the rail. This can be used as an automatic switch of sorts. When the train's wheels cross it the wheels make a connection from the other outside rail and the circuit will be completed and the accessory will work as long as the wheels are crossing the insulated portion. By doing this on only one side and using the lockons on the other side you have a complete common rail with no disconnects.

Ron

This is very normal with RealTrax switches. They have anti-derail built in, one outside rail on each connection is isolated. When a train touches that rail the switch moves to that position. So if your outside rail is the one that the switch breaks you will lose power. I always add a power drop after a switch unless all switches on a loop point in, or all of them point out. Then you can just use the other outside rail with one power drop.

However, I never make such a layout except my Christmas loop.

So in general, a power drop in between each pair of switches is in order.