It did for me (on a Mac though, and track pad so it was double press). I swapped block and jump, so spacebar now blocks and RMB jumps. Took me about 2 runs to get used to it, but it works for me.

I've had this issue here and there, no idea why it happens. Could be lag but idk. Its also really hard to document because obviously I can't prove I was still holding up block. I do notice it in conjunction with certain skills being fired on me like meteor especially. But not always.