Wheels falling off the Blaze

[Jonesy]

Evening....

After running the Blaze I have had an issue with the Mi4 wheels coming off and leaving the 2.6 x 10mm screws in the Hex. I have tried to conter this problem by using washers and increasing the screw length to 12mm but the wheel still fell off, possibly as I haven't got 'correct' washers.

Any thoughts on a solution without replacing the driveshafts. Are the 10mm or 12mm screws sufficient or is this a common problem without using the nut?

Thoughts and guidence on what others use would be welcomed