IsFullyCharged only works for the Base Tier of the ability, with Tiers 1-8, the ability will stick and not cast even when it's fully charged.
In regards to the Charge Shot spam, enable the combat option, "For relevant abilities, press and hold a key rather than double-tapping.
Hold down '1', and have it Cast a Full Charged Shot", keep holding down '1' and once Charged Shot goes off cooldown again, it'll start spam tapping it.
Occasionally it casts normally, and other times it spam taps. The only way to fix it in all cases is by toggling that option off.
In regards to the Charge Shot spam, enable the combat option, "For relevant abilities, press and hold a key rather than double-tapping.
Hold down '1', and have it Cast a Full Charged Shot", keep holding down '1' and once Charged Shot goes off cooldown again, it'll start spam tapping it.
Occasionally it casts normally, and other times it spam taps. The only way to fix it in all cases is by toggling that option off.