I also partially bored out the end blocks and added some needle roller thrust bearings on each side of it for the friction years ago.What happens nest is those brass inserts fail, or rather the plastic around them does, due to the additional force you are pushing through them.
I bored out the end blocks behind the wheels and fitted two deep-groove flange ball races - massively reduced the effort required. And fitted some small aluminium hand wheels bought with a pilot bore from WDS.
If the handles fail I'll just make new cast ones, this was just a quick and simple fix which should last me for a long time.