New produced Mantis should have this fixed already, they have a very tight fitting hinge as suggested here! Check with your dealer!

To prevent that force that breaks the bolt you need the tightest fitting (most important) and longest hinge piece possible.
A sleeve would not help if the hinge does not have a tight fit because the bolt would still break between hinge and sleeve so there is not much point in the sleeve.
To fix the little gap remaining between cylindrical hinge part and its tube you can use cling foil or loctite 638
(or similar "retaining compound" glue from other brand that is locally available).
If you fix the hinge good enough that it cant move even if there was no bolt holding it then the bolt will never again break (because there simply is no more force on the bolt).
The bolt breaks because of force to the side that would bend and wear it.