Glo Strange display behavior

Well, here's the story.
Yesterday I took my Glo out of pouch (it was in there for 2 days) and wanted to connect it to my PC.
When I went to USB menu (i'm using KSM) i've noticed that screen refreshes in a very strange way - fills the border first, then the whole screen. That also was very slow and had a lot of ghosting.
I was unsure if it's software problem or not, so i went ahead and did a hard reset and Wi-Fi setup (it updated to 3.13.1 over wi-fi).
Problem though was still there, even after HR.
I was kind of worried, maybe i broke the glass or something?
So I uploaded a pic and opened it - no "bad" spots on display, picture looks great.
After numerous tries to fix that, i've just put device to sleep and went to sleep myself.
In the morning I've powered on my device - and it's working fine, like nothing of the yesterday events ever happened.

So here's my question - what was that? How do I avoid that in the future?
Maybe e-ink displays can't tolerate temperatures over 30 (celsius)? Or maybe my device was laying in pouch "upside down", display facing "table"?
Thanks in advance.