slipping clutch in 4wd

Hi,
The clutch on my 2009 4 cyl 5 speed sometimes slips in 4wd, both high range and low range, usually briefly - a second or two. This started around 80,000km (50,000 miles) in low range while backing up. Most recently (92,000km), in high range, while turning around on soft gravel road.
The truck is used on Vancouver Island logging roads while pursuing caving/karsting activities Four wheel drive is used occasionally, only for short periods of time. Clutch does not slip in 2wd, at any speed.

 

It's probably fine. I've stood on mine to get the truck up some rocks and it's still going at 220k km I've had it slip in 4wd before too not overly concerned until it starts in 2wd