Hi - I can confirm the existence of this problem in my Boox. I received it from a European web shop at May, 11th.
When exposed to direct sunlight, it only refreshes partially when I turn a page. The new page is absolutely unreadable. If I take the device back in the shade and refreshes, the page is OK.
I have sent an e-mail to the shop explaining the problem, but I'm a bit concerned I haven't had any response yet.
And, sadly, this is
not the only hardware problem, I have had with my Boox.