When right-clicking a tamed Grizzly Bear to either apply or remove Snow, if sneak is not held the Bear will be mounted with the same action. If mounted this way, a desync occurs as shown. Regardless of visuals, the player and Bear's positions are locked to where the Bear was mounted, and it cannot be dismounted. A relog is required (or is at least the most obvious way) to remedy this state.

Mods:
Alex's Mobs (1.22.9)
Citadel