I've noticed this quite a lot. I jump, I press the glide button (a.k.a jump again), the sound occurs indicating glide start, but the character keeps on falling. This is a bit annoying if you're trying to glide across a chasm or some such. By the time you realize you're actually falling, it's too late. You survive but you gotta climb back up.
Hi there,
Thank you for bringing this to our attention.
To confirm, are you using a specific umbrella when this happens, or have you experienced regardless of what kind of glider?
Do you use any other keys such as [F] or a custom binding for gliding/jumping?
Does the character have sufficient stamina when this occurs?