It is, mine does it on and off. I find a fluid change helps for about 5,000 miles, then it starts again.
It's a sign that it really needs a rebuild, which I'll get round to at some point.
I suggest you call Bell Engineering to ask them what to do next.
Here at LandyZone we have plenty of very knowledgable members so if you have any questions about your Land Rover or just want to connect with other Landy owners, you're in the right place.