Could it be the 225 MGB Design failed to correctly assess Loading on those particular Gears/Bearings? Sometimes it is more an art form than science when trying to determine the true loading of various parts of a helicopter.
I am just suggesting there is more to designing a piece of machinery than meets the eye sometimes and we discover that limitation the hard way far too often.
Some examples....the US Army lost two UH-1's and Two Instructors and Four Student Pilots in one day due to Tail Boom failures at Fort Rucker. That led to needed Mods to the Tail Boom.
PHI in the Gulf of Mexico lost two Jet Rangers due to Transmission Mount failures in one day.
The US Army lost a couple of Chinooks to Incidence Bolt Failures on Rotor Blades.
Sikorsky had Blade problems on the A Model 76.
The Wessex had some gearbox failures.
It is not limited to just one Brand, Type, Model, or any one set of Engineers.