[OS X TeX] strange behavior of TeXShop in macOS Sierra when using multiple languages

[Alessandro Andretta]

Dear all,
I am testing MacOS SIerra version 10.12 Beta (16A286a) and I am using TeXShop 3.65  with TL2016. 
The primary language in the System preferences panel is set to English, the second to Italian, and ever since I tried SIerra I noticed the following strange behavior. 
I open a LaTeX  file and the spelling and grammar window sets itself automatically to Italian; since it is a document in English, I set the spelling and grammar window to English, but as soon as I click on the pdf, the spelling and grammar window moves back to Italian.
Has anyone noticed a similar misbehavior? This bug does not seem to affect other apps, like e.g. TextEdit.

Regards,

	--aa

P.S.: I already used the Feedback assistant to notify Apple.