Occurs when you get hit by a 1/1. From what I've seen, if you try to remount too fast after the hit, your skills get locked despite having enough mana to cast anything. Pretty annoying during Shao.
It is more to pet auto pot's issue, pet always prior to consume your potion on Auto HP pouch try replace your potion on HP pouch with Elixir or whatever potion that gives both HP&MP~ Hope this helps.
Nope, it's not about MP autopot. The original description is pretty accurate. Can't mount again even with full MP. I had to walk around, use rapid fire and even type '1' to get back mount.