how to keep screws on

[Serum]

Normally a wheel getting loose might be another problem; the blue nylon part in the nut is worn out (these nuts are actually meant for 1 time use only)

or the hex is sloppy on the wheel or on the shaft. or the wheel is wobbling like crazy..

Normally, the wheels don't fall off for no reason. If you can't put your finger on it; go for the blue loc-tite solution.