Your error log does tell you the reason, it’s the part about:
Refused to display … in a frame because it set to ‘X-Frame-Origin’ to ‘SAMEORIGIN,DENY’
And the reason for that is the one about “conflicting values” before it.
WordPress core only sends SAMEORIGIN value in admin screens, via send_frame_options_header(). So DENY is coming from elsewhere and is what messes things up.
Search your sources for DENY and inquire with hosting support if it’s something web server might be configured to add.