APEX 20.1.0.00.13 fails to load the resource file "custom-elements.min.js.map".
It tries to load the file from the following path:
[images_directory]/libraries/apex/minified/custom-elements.min.js.map
But the correct path should be:
[images_directory]/libraries/oraclejet/8.0.0/js/libs/webcomponents/custom-elements.min.js.map
(As a workaround, the file could be of course copied to the desired (wrong) location.)
Best regards
Robert