UPPERCASE letters only - why?

Maybe I have done something wrong, but question is : Today I continued writing a document (diary) which has ben OK up to now, but my writing today was all in UPPERCASE. I switched the uppercase key on and off, but no difference.
I guess I must have hit a combination of keys, but which ?
I also tried to create a new document, and in that one everything was as it should be - Uppercase key on = uppercase letters, Uppercase key OFF= lowercase letters.
Any idea?

Share a sample file. Otherwise, it will be only a guesswork.

Does this only happen LO, or is it also happening in other applications? If everywhere, then you’re keyboard might have a problem. Else if just in LO, does closing and re-opening LO help or change this?

If the keyboard setting does not change the UPPERCASE input, you could have an unintended font effect setting.

Check that you do not have the FONT EFFECTS setting to Capitals or Direct formatting set by mistake.

a) Select the area you wish to check and then CLEAR DIRECT FORMATTING (ctrl+M) to see if that does anything.

b) Also you could try > select the area then right click, select CHARACTER > FONT EFFECTS > WITHOUT then OK. This will clear any unintended font effects.