Why are some symbols displayed incorrectly (squares) when loading formulas from MathType in LibreOffice?

Question

Character encoding

Good afternoon.
When loading formulas from MathType in LibreOffice, there is a problem that some symbols are displayed incorrectly (squares), such as the sum or integral sign.
How can this be cured? Maybe there is another way to insert formulas.
The internal editor is not suitable.
Thanks for answers.

Answer 1

What software versions are you using?
If everything is really sad - insert pictures. The most extreme option is Print Screen -> Ctrl+V .