2003 jimny jumping out of reverse

Hi new to the forum and need some help

We have a 2003 jimny 1.3 special with 56000 miles on the clock

Completly standard and not used off road

It has developed a problem with reverse gear

After selecting reverse gear you can drive the car back a metre and then it will jump out of reverse.

Every other gear is fine and no grinding noises at all. All gears are nice and quiet

It will select reverse nice and easy.

Can anyone help me diagnose this problem please

Sounds like a worn gate in the syncro , but may be something more simple .
Lift up the rubber boot and and check for anything obvious like worn or bent parts also try get under the truck and check the gearbox mounts are all ok and nothing is caught under there

cheers will have a look