PureLine R2 Pool Cleaner

one of the wheels fell of my PureLine R2 Pool Cleaner and it was doing circles in the bottom of the pool.  Reattached the wheel and it’s working great.  any advice on how to keep it from happening again?  Also, can I get parts, like new tires for the R2 on your site.  The Pureline R@ is a little more work, but for the price - it’s awesome…

Tim