First, let me say I know absolutely NOTHING about controllers.
However, I do know that if you have stranded wire and it's fraying so you cannot insert it where it needs to be, you can "silver" the ends with solder.
No wait- DON'T PANIC!
It's actually very easy to do. I was scared of it before I did it the first time, too.
If you buy a mid range priced soldering gun "kit" with the flux and silver included, it will most likely have instructions included that will tell you how to silver wire.
Basically, you touch the soldering iron to the wire end first to heat the wire, flux the wire, then touch the solder to the wire and it just sucks into the wire.
Let it cool and you have a nice solid end that's easy to mess with.
Solder kits are at Lowe's, Home Depot, good hardware store.
Brian