[Windows/Steam] Slowed, Unable to Cast Spells After Self-Buff (Cleric/Mage)

Hylius

While playing as a Cleric/Mage multiclass with armor equipped, any spells that buff my character that I cast (reproduced with Draw Upon Holy Might) have a high chance to slow my character's movement and leave me unable to cast any of my spells (including Cleric ones). I

1) Start multiplayer session.
2) Cast Draw Upon Holy Might
3) Observe that you are slowed and all spells are grayed out (quickspell slots also empty)

Note that the above is not 100% reproducible. Have not determined a 100% repro method yet.

Expected:
Should apply the proper spell buffs without any drawbacks.

Notes:
1) Have not attempted this without armor equipped.
2) I have been playing solely in online multiplayer.

Edit: I removed the references to Chant, as it is supposed to do that (and I'm guessing why others are doing the same thing). I didn't realize it was modified from the BG2 version that I'm used to.