Spell check won't see the word as a whole, says part of the word is wrong

[AP1998]

This happens almost every time I delete a letter from a word and then rewrite it. In this case it was written "design" so I deleted the "d" and wrote "D" again (with capital). Now spellcheck won't check the whole word, only sees "esign"

[#2]

@AP1998 What proofing language are you using?

Here with English (US), word indicates a punctuation issue if I press Enter after Intended Research design

and a spelling error if I delete the d of design and then press Enter after that word.  However as soon as I insert the D, the spelling error indication disappears.

[#3]

I am using English (United Kingdom), if I switch to English (US) the issue dissapears. It doesn't persist if I go back to the original proofing language. I suppose if I encounter the issue again, I'll just do the same again to fix it. Thank you

[#4]

This recently started happening to me recently, too, but switching proofing languages does nothing to fix it; I've tried going from English (Ireland) to both English (United Kingdom) and English (United States), but to no avail.

[#5]

@rcoady Here, with the proofing language set the English (United Kingdom) without the "D" of Design, the word is flagged as an error.

If I right click on the error, I am offered the following corrections

However, ignoring the offered corrections, as soon as I insert the "D" at the beginning of the word, the indication of an error disappears

Can you share a copy of a document in which you encounter the problem.

[#6]

@rcoady 

The proofing language is applied at the character level, not the document or application level.

Select all your text and apply the proofing language.