That is not normal, then. It's possible there are globs of solidified grease causing the mount to stick when rotated past the usual limits of movement.
My impulse would be to pull the mount apart, remove all the old grease (aka 'glue'), check all the bearings to make sure they're not clunking (and replace them anyway) before re-greasing everything.
I did all that to my HEQ5 when it was only 3 months old. But then, I'm that sort of spanner-waving tinkerer.
Cheers,
V.