you need to jack the back end of the truck up , operate the steering , identify whether there is any play in the steering and resolve this. Once all the mechanical checks have been carried out e.g king pin play etc. You need to adjust the steering stops. Failure to adjust the steer stops correctly will lead to excessive loads being applied to the wheel hub bearing when driving or reversing the truck with large amounts of steer angle (ackuman's principles of steering & basic physic's).

Its a Doosan, pro 5 range.

Has anybody had any issues of rear wheel bearings collapsing and wheel falling off ?

All bearings, pins, and links previously replaced.

Any info appreciated

Tyres not worn unevenly

What make of truck is it?

Have you checked if there are any replaceable bushes for the steering links? done some the other week on an old Hyster, also done them before on BT / Cesab machines.

Some makes are a lot easier then others to replace these bushes on.

Possibly if they were quite badly worn, as when you drive forward the wheels could both toe outwards causing side loading on the wheel bearings and vice versa in reverse. Are the tyres unevenly worn?