Characters not displaying properly in Libre Office latest version

After upgrading Libre Office from ver 5.0.6 to 5.1.5 and then to,
I noticed that many characters are faulty.

For example:
In Calc:
In the columns’ headings: A, B, C, D, etc.-
B → _ (underline),
D → a,
H → e,
J → g,
O → l,
W → t,
AB → A_,
… and so on.

In the rows’ headings: 1, 2, 3, 4, etc. -
3 → P,
6 → S,
13 → 1P,
…and so on.

Also in other places in the program these errors occur.
And also in other applications of Libre Office.

I must say that I’m using a version with Hebrew Language,
I suppose the English version is clear of this bug.

I’ll try to uninstall Libre Office and then reinstall this time in English somehow

I tried uninstall and then install,
the bug is still there though less.

I changed language to English,
with assistance from here,
and didn’t help.

I did notice though, that when I enter Libre office from the icon in the start menu, the bug mostly disappears, but when I open a file from desktop, the bug appears

The file itself was causing the error somehow
(maybe because I had started it in an earlier version of Libre Office).
I recreated a new file, saved it on desktop, and now it’s ok.
Still there was some bug which caused me all this fuss.
Hope this post is useful to anyone

Just wanted to add that a book I’d written in Apache OpenOffice and opened in LibreOffice had what appears to be the exact same problem. It’s written in English, though it also uses combining diaeresis (U+0308) and a combining double inverted breve (U+0361) in places. I initially thought it had loaded fine but had to notice now that I’ve started editing that it’s changed various words of my conlang (e.g. “Jabenash” is now “gabenash”).

That said, it seems to be a pure display issue - I find “gabenash” if I search “Jabenash”. My solution will be to (re)install Apache OpenOffice and do my editing there (I still have unadulterated saves from the last version there) - I don’t trust LibreOffice with Apache OpenOffice files at all now, and after two years of working on this book I’m not willing to risk overlooking a problem that might persist into an export as an ebook.

If it helps anyone interested in diagnosing the error: While I can’t guarantee it, I think only my conlang is affected. It uses a different font (Arial) than the rest of the document (Verdana), and the UTF-8 characters I mentioned are only ever used in the conlang format-style. So in my case, it’s possible LibreOffice is switching to some other display mode for that style, triggered by the combining UTF8.