We are currently one major release behind in Swagger OpenAPI.
https://github.com/swagger-api/swagger-ui/releases.

Upgrade it to latest version according to documentation available at https://github.com/swagger-api/swagger-ui#general.

download the latest release and copy the contents of the /dist folder to your server.

Our server is located here: https://github.com/opendaylight/netconf/tree/master/restconf/restconf-openapi/src/main/resources/explorer

Don't forget to keep our custom changes in UI.
https://git.opendaylight.org/gerrit/c/netconf/+/106150
https://git.opendaylight.org/gerrit/c/netconf/+/105219