Highlighting very slow in LibreOffice Writer (v. 7.0.3.1 00)

I have a relatively small document (~10 pages) with several reference marks within. No images. When I try to highlight text, the document lags for about 1 second and then shows me the highlighted text. What can I do to speed LO writer up?

Using Ubuntu 20.04 LTS.

Thanks.

Still haven’t solved this issue: Dec 27, 2020. Thanks.