0-4-0 gear slip

[gscalerr]

Is there a fix for my porter gear slip on the axle? This is the little gear on the axle. Thanks 4 any help.

[mudzuks]

I clean the area very well with alcohol then I dip a very fine point paint bush in green lock tight and dab it on the axle, the green is the lock tight for after assembly it gets and then dries and has stop a similar problem I had with a different loco

[gscalerr]

thanks for the help. I have now found :'(a minor crack in the gear. Are they available?