[TW5] Tiddlywiki "Check Spelling" and Firefox - not working

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Hi.
I have problem with spell checking.
I downloaded single file version (the empty one) for Firefox.
In Firefox I have enable automatic check while typing (and it is working for example on this forum while I typing this post).

But when I edit tiddler and write something wrong it is not underline with red line.
Also when I edit tiddler and click RMB on that word I have "Check Spelling" item (unchecked) on dropdown menu but when I LMB on "Check Spelling" whole menu disappears but this item is still unchecked .

Firefox version: 51.0.1 (64-bit)
Tiddlywiki version: 5.1.13

Language tiddlywiki settings: English (British) Dictionary in Firefox: United States English Spellchecker 8.1

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Codemirror plugin was the issue.
After disabling every thing works fine.