EDIT: The first link should be https://developer.apple.com/documentation/appstoreconnectapi/modify_an_app (not "modify_an_app_info"). The last link is correct.

Glad to know I'm not the only one with this issue! I've submitted a ticket as well as a bug report on their Feedback Assistant, but so far no progress for this issue.

Just an update, Apple applied a hotfix which seems to have resolved this issue!