Autoattack Bar getting stuck sometimes!

[Rittmeister64]

hi guys.
one annoying thing I notice especially on my druid is the autoattack bar gets stuck at 100% and does not refill, despite melee or ranged button is still active.
Why does this happen, and is it just cosmetic (meaning autoattack is still doing damage) or has my autoattack actually stopped?

I know, on my SK, when this happens it is because i press skill buttons to quickly and dont let enough pause to make autoattack activace, taking a short break will fix it in this case, not so on my warden.