I call "problem" a problem when situation can not be resolved at all, but you don't have to worry. It was only very little few faulty reports that could not be resolved remotely and warranty exchange was swift by vendor, but this is the last resource if can not help now.
Pano uses high quality glass lens so hot sun could not damage ( melt ) top layer, so this idea I keep away.
The only I might think is that glue that holds lens thread in fixed position after focusing, - it was not enough applied and got melted, resulting in lose connectio nand after soem driving ( vibration ) the lens went out of focus.
It happened to me in the past with one cheap chinese model.
Problem resolved by adjusting focus manually and put some extra glue over thread, not super-glue
, but in your case because it's under warranty, please first consult seller what to do. You send it back for replacement, or you want to try to adjust lens yourself, with agreement that if you can not manage to fix and still send it back, - they will not void warranty because of you trying to fix yourself.