Dash costs no MP

Description of the bug: (optional screenshot/video): When using Dash at max level the MP bar appears to go down as if it costs 5 MP like normal, but the next time your MP is updated from using a different skill or drinking a pot, all MP that appeared to have been spent on Dashes is restored. Seems like a client/server disagreement
What is supposed to happen?:Should use up the 5 MP (or more at lower levels)
Where did you find and/or notice this bug?:I only noticed it at max level Dash, but it may very well apply to lower levels too
A step-by-step guide to re-producing this bug (optional):Use max Dash and wait as your MP regens 8 points instead of the normal 3. You can spam lots of Dashes and all of it will regenerate, +3
Extra information (optional): It's kinda convenient to dash everywhere freely, but I'm guessing it's not intentional.