I just tried cramming a lesson from my custom list, with the word 天氣. Strangely, it appeared as 天气. I have only enabled traditional chars, and this is the first time I have seen a simplified char show up anywhere...
Maybe just a glitch :)

Looks like a bug with the variant character handling (气 here is also a traditional character by itself when talking about the radical 气). Which custom list is it?

I created this cramlist (cram?list=agVza3JpdHIRCxIIQ3JhbUxpc3QYm8ytBQw) from Lesson 2 of my published vocab list (vocab/list?list=agVza3JpdHIWCxINVm9jYWJMaXN0SW5mbxiN6ocFDA)

I happened again, in another cram list. The word 週末 in the list, ended up as 周末 in the cram list...
( the list is agVza3JpdHIWCxINVm9jYWJMaXN0SW5mbxjh160FDA, the cramlist is agVza3JpdHIRCxIIQ3JhbUxpc3QY36vGBQw)

Ah, I see what's causing this bug. Looks like it isn't quite a quick fix; I'll confer with Scott about it when he gets back from a wedding.

Thanks for the clear examples!

Thankfully, it was possible to edit the cramlist, so being aware of this issues just means I have to verify the cramlist and correct any mistakes; so at least a work-around exists :)

I decided today I had a whole lot of quick fixes to be done that have been waiting around far too long. So I fixed this one, and many more minor adjustments to come... Sorry this took so long to get around to! I'll be working on prioritizing better from now on; little things like this should just get done quickly.