I don’t know if this effects all classes, because I only play my Engineer, but I suspect it might be Engineer specific because of many Engineer utility skills being bundles which effect your 1-5 skills.
The bug exists while using siege equipment, where if you change a utility skill you have equipped, you lose the siege equipments 1-5 skills and cannot get off the siege equipment at all.
It results in the player being unable to attack or move, and can only be cleared by waypointing away.
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