It occurs after the 1.15.0.51 beta update and is reproduced 100% in the following way.

However, this bug can be used normally when first taming a horse and occurs when trying to use a tamed horse.

1. Tame the horse and place the saddle item on the horse inventory.
2. Make sure your horse is in control
3. Remove the saddle from the horse
4. Get off the horse.
5. Take a moment. Or spend the night.
6. If you ride a tamed horse while the saddle is in inventory, the inventory open button (E) does not work. Riding a horse does not open its inventory.
7. Exit the game and turn it back on to open the inventory. However, if you still ride the horse inventory button (E) does not operate and the inventory of the horse does not open, it will burst.