I have 2 cels having that mouth problem, one I 
haven't scanned yet, and the other one is the 
one I offered for trade/sale a few weeks ago. I 
didn't know that detail at the time because I 
hadn't watched season 3 until recently and this 
is when I got the screenshot. Here is the pic 
again.

Also, I think my background is unmatching if I 
refer to my screencaps, although my cel is still 
sealed by Toei. Does that happen often ?

With all those differences, could it be possible 
that a particular pose could be used in 2 
different episodes even if it's not a bank cel ?

Thanks ! As you can see, I don't collect SM cels 
a lot, so any help at all is appreciated ^-^. 
This really sounds like a big mystery to 
solve ;).