Can permanantly degrade movespeed casting after blinking (100% repro included)

It is possible to permanently induce the movespeed penalty on the character caused by casting by quickly blinking away during the cast.

Prerequisites based on my character (but may not be necessary):
a) Have Blink on weapon swap.
b) Have high cast speed
c) Use spark (though I suspect any spell will do)

Steps:
1) Right click and hold spark until your character is at maximum movespeed penalty. Note, you do not actually need to move, you can stand still, just cast for a full second.
2) While holding right click (you're still casting), simultaneously weapon swap and cast blink in any direction.
3) Immediately on arrival release the right mouse button and then left-click once.
4) Character may never recover from the movespeed penalty and will walk around with it forever.

This may take a few tries, but the accuracy of reproduction depends on how quickly to follow steps 2 and 3.

I can provide a video if necessary. I can reproduce it in 1 in 3 tries. Message me if it's needed or helpful.

Even easier repro steps:

1) Weapon swap to weapon set 2 and blink.
2) Quickly cast one spark (weapon set 1)
3) Quickly click to move

Almost 100%.

Bump. This is regularly a pain.

Also reproduction update, don't even need to weapon swap.

1) Put on 35% movespeed boots.
2) Blink
3) Quickly cast Spark once

Movespeed will be degraded until casting again.

Still happening