I had the same issue and opened a ticket. Apparently this is a known issue and there is a fix in Xanadu and a possible hot fix releasing today -
Issue:
Javascript error on ESC after upgrade to Wash DC
Most Probable Cause:
This is a known issue, please refer the PRB1758577
https://support.servicenow.com/kb?id=kb_article_view&sysparm_article=KB1644179
Solution Proposed:
This problem is currently fixed in the Xanadu Release, and is currently tentatively targeted for a fix within the "Washington DC Patch 4" and "Washington DC Patch 3 Hot Fix 1" release. As of now, there is no functional impact of this PRB.
If you wish to suppress these errors as a workaround, the property "glide.sp.show_console_error" can allow you to achieve this. These errors are governed by the above property, and are only displayed to admin users (even when impersonation is used). When a non admin accesses the portal (through a direct login), they should not be able to see the errors. Disabling this can allow you to suppress the messages for admin users, however this will disable all javascript errors:
https://docs.servicenow.com/bundle/tokyo-servicenow-platform/page/build/service-portal/concept/prope...
Alternatively, upgrading to Washington DC Patch 3 Hot Fix 1, which is currently targeted for a release on the 20th May, can also resolve the issue faced.
