Alright, I don't know if this helps, but I've just discovered that the casting bar disappears for non-songs too. Ie, if you use a clicky effect like on pegasus feather cloak, the casting bar will sometimes disappear and the spell will still cast at the end.

I get this all the time. It becomes more frequent the harder I am trying to twist, so it might have something to do with how quickly you cast one song after the other. Likely only happens to bards due to the fact we don't have any recast timers.

I saw the casting bar disappear on my mage, when I was testing some other things. It is probably related, but bards are just clicking the spell gems more. I have some ideas of things to look at now. Since it is common to both bards and regular casters. When I get back from vacation, I will try to figure out how to fix it.

H

The bard spell bar disappearing happens on the SoD server too, which uses an older client.

My guess is that it's tied to lag between when you do something in the client and when the server gets the info.

Say you tick and switch songs; the tick goes into the server some point in the future, and presumably the server responds to your client with relevant information. Maybe this response interrupts what you are currently doing from the client's perspective. The songs still go through, casting bar gone or not.