When I open the matlab help doc, it shows correct content at first but turns blank after a while?

Operation system: Ubuntu18.04 LTS

matlab version: R2020a

Everytime I start matlab and open help doc, the content can show correctly but disappear after a while. I have searched a lot in the Internet but got no answer.

Some possible reason maybe that the jxbrowser-chromium document does not exist after installation, becauser some possible answer explains that the dir of jxbrowser-chromium is necessary for the normal display of help doc. I don't know whether it is correct. Hoping some one can help!