Bug in saves created while mounting the horse (Frost)

[dragonvale]

After more than one hundred hours of gameplay, "finally" I've stumbled in the first bug.

 

Every time I load a save made riding Frost, he begins to spin and fly. New saves or quick saves make no difference.

 

With another character (different NMM profile with same mods except for Eli_Breezehome & AP) I can save and reload without any issue.

In both NMM profiles, I've 2 mods related to horses : Essential Frost & Shadowmere and Whistle

 

The only difference is that in the playthrough where this bug occurs these mods were installed before start a new game,

while in the playthrough "bug free" I've installed both only after getting Frost. Can this be the cause?

 

Any suggestion is welcome, thanks!