Has it been reported that Fulmination is going off after anytime more then 3 stacks of lightning shield are active? It should just be going off when it is fully stacked at 9 stacks. Also Lava Surge isn't coming up as a reactive spell when Lava Surge proc goes off.
The lava surge part is bugged yes, however fulmination is not bugged. You can use earth shock whenever you choose to, and if you have more than 3 lightning shield charges, it will consumes the surplus and deal damage to the target. The animation part of it is bugged however, you should only get the animation once you hit 9 stacks of lightning shield.
Ye you can use surplus lightning shield charges whenever you feel like, i often do so at 6-7 since its easier to finish people off with lavaburst/earth shock than trying to get full 9 stacks alot of the time