Actually we identify the issue:
thanks to Rlorenzo
he fixed the same issue like this issue. The reason is as follows:
Moodle's RTLCSS script fails to properly parse the following CSS:
border-radius: 0 100% 100% 0 / 50%;
Thus create new lines that follow that should produce the same results as above.
To duplicate the error run the following script:
php admin/cli/build_theme_css.php
On our Moodle 3.4.4 system we got the following errors:
php admin/cli/build_theme_css.php
== Build theme css ==
Default exception handler: Exception - Call to undefined method Sabberworm\CSS\Value\Size::getListComponents() Debug: