Math: How could I get Sum, Product and Integral operators as a "Liberation Serif" symbol instead of "Liberation Sans"? (v5.0.6.3)

All fonts for variables, functions, numbers and text are set to “Liberation Serif” plus attributes.

The operators for Sum, Product and Integral have a different style from the Coproduct and the other Integrals.
I would expect the Sum operator to be same as %SIGMA, with a “Liberation Serif” style, but it is shown as a “Liberation Sans”, for example.

I tried to find the options for the text/symbols used for the operators but wasn’t able to locate anything like that.

How could I fix this issue and have them all as “Liberation Serif” symbols?

Update: I edited the document in 2 different computers, back and forth, with the same version of LibreOffice and I got the right font once. I created the document in one running Win 10, edited in another with Win 7, edited in the first with Win 10 e again in the other with Win 7, when I got it right. Now I’m back at the Win 10 computer and it’s back with the bad font again… Bug of some sort?

Have you ensured, that the font OpenSymbol is installed?

Yeah, it is installed but also seems to be corrupted. After opening the “Special Characters” window, it shows the wrong symbols exactly for U+220F (product), U+2211 (sum) and U+222B (integral).

It seems it’s quite an old problem: Formulas look weird on certain computer?
The font rendering under Win8+ is not working properly.
Someone changed the OpenSymbol to solve it: [Solved] Symbols font on Windows 8.1 (View topic) • Apache OpenOffice Community Forum

The font used for operators is OpenSymbol. You should not change it, because it has got a lot of characters, which are not available in other fonts. But you can add a definition to the symbol catalog, that uses the font and style you want. If you have named the symbol “mysum”, then you can make it a large operator by using the keyword oper, e.g. oper %mysum. A “large” operator is a operator, which can take the keywords from .. to ...

Thanks, I already tried that and it works, but it is a workaround I wanted to avoid. Actually, the bad font isn’t something essential, so I’m just using the regular symbol anyway for now.

By the way, sometimes the symbol is shown with the right font at the Math interface… May be a bug to be submitted later. Just trying to rule out something more obvious on my end before that.

I’ve realized it’s a problem with OpenSymbol under Windows 8+ and it’s not actually a new problem:

One solution was to patch OpenSymbol itself, going around the rendering problem: [Solved] Symbols font on Windows 8.1 (View topic) • Apache OpenOffice Community Forum

There are already bug reports on this issue for quite some time with no apparent solution:

For now, I’ll just use a custom operator as a workaround whenever possible.