My horse is broke

I am in the process of doing The Hunt quest when you hunt down Ginger but my horse has broken. I can mount it, but it won’t move. It’s frozen. I can get back off the horse and call it. I have checked the weight and the horse is carrying a few tiny things. But it’s just not shifting. I only just got the thing. Had anyone else has this?

Also have this same issue. The horse seems to be not functioning correctly now, after working fine for previous hours of gameplay.
Can whistle for the horse and it will come. Can mount the horse–but it won’t move, gallop or trot. Horse has some items in it’s inventory, but not over weight.
this is an incredibley moody horse and he is refusing to move an inch while mounted.
The horse is ‘Pebbles’ received as gift/first horse.
Any suggestions?

Update: Today is a new day.

Pebbles rides again!
The following morning the horse riding functions have returned to normal.

The temporary ‘bug’ worked itself out after sleeping in the owned bed overnight (in game)