E-Revo wheel nuts getting loose, falling off. Fix?

[simplechamp]

I have a problem where my wheel nuts (just the 5mm nuts, not hexes) are getting loosened during driving. Finally tonight a wheel fell right off so I really need to fix this.

It seems to happen more on the front wheels, but the back wheels suffer from the issue also. The nuts are flanged nylon-insert lock nuts. The front 23mm hexes now seem to be damaged from driving with the wheels loose (before I noticed the problem of course). I have other hexes that I'm going to install once I get a 23mm hex wrench, so I was just keeping the old ones on until then. Doesn't seem like the hexes would cause this issue. See pics (front hexes only, rears are in perfect condition)

Should I buy new lock nuts and see if that fixes it? Or are there any other issues that could be causing it? The stock axles will soon be replaced by CVDs so I don't know if that will have any effect?