Created attachment 120052 [details]
The image shows the formula editor's bugged element selection menu where the most bugged elements can be seen.
This bug appears in the formula editor and within the document. Have not tried printing yet. For example, this bug replaces the equals (=) sign with a 5,25" floppy disk, in the formula editor selection menu and the document.
This shows that OpenSymbol font is missing on your computer and wasn't installed by LO 18.104.22.168. You can verify this first. Next, the best is to uninstall and install again this version, to see if this solve the issue, as in this bug report.
See Bug 95289 - The display of mathematical formulae is erroneous in LibreOffice Writer documents.
Reinstall fixed it,
Thanks a lot.
*** This bug has been marked as a duplicate of bug 76239 ***