This happened to me several times during my run on Cooper Roost.
-I teleport to Cooper Roost with me riding a Lonely Buffaloon. -I tried moving through the rock bridge only to get stuck on the edges of the bridge. - This results in me teleporting to Skull Island to try again.
I don't know if it's a Lonely Buffaloon hitbox issue or an universal mount issue. Either way, I'm addressing it.