Proofing language keeps switching automatically

Question

Some of the text in one of my documents keeps changing its proofing language to 'Arabic (Saudi Arabia)', despite the fact that:

1. There is no Arabic in the text
2. No Arabic input method is installed on the system
3. Arabic is not installed as a proofing language
4. I've set the default proofing language to English (UK) in File>Option>Language
5. I've changed the proofing language of the Normal style to English
6. I've selected all text with Ctrl+A, changed the proofing language to English and turned off automatic detection of languages
7. I've cut-and-pasted the entire text into a new document.

That's about all I could think of.  In "Arabic" text, it is impossible to put text into Italics, and the text can't be checked for spelling or grammar. The basic document was based on a Style sheet delivered by a publishing company, so I expect something is wrong with some of the styles, but how to solve this.

Answer 1

Note that even after you have turned off the auto-detection of languages, you still have to fix existing documents manually, by selecting text and (re-)applying the correct language. For affected documents, you should also modify the language of the Normal style.

Answer 2

If you send me a copy of the document, referencing this thread in the covering email message, I will investigate the issue.