There's a bug that causes sprites to use the wrong skill, and then keep using that skill on cooldown until you finish the floor. The bug is caused when multiple mouse buttons are pressed together(ex. moving forward with left mouse and using a sprite skill bound to a mouse button).
In my case I have Sprite Skill 1 bound to mouse button 4 and Sprite Skill 2 bound to mouse button 5, pressing either mouse 1 or mouse 2 in conjunction with mouse 4 will result in the sprite instead using the skill bound to mouse button 5, and the sprite will continue to use the skill whenever your character is not busy, preventing you from using other sprite skills, shielding, or attacking.
The chain of spam part has happened to me several times, except I don't have any sprite skills assigned to mouse buttons. It happened yesterday to a party member at the Roarmulus Twins. His Drakon kept messing up my operation of the switches by spamming its primary attack (causing an inexperienced party member to die more than he otherwise would). I think my sprite usually starts the chain if I press the skill button a few times before the cooldown timer expires.
I have found that the spam chain can be broken by pressing F2, then Esc. But it can just as easily start up again.