Contribution Edit: Buttons Missing (MutationObserver Error)
On 5.73.0, when clicking Edit for a Contribution, no save/cancel buttons are shown on the popup window. In the browser console, we see this error (pointing to crm.ajax.js as the culprit):
Uncaught TypeError: MutationObserver.observe: Argument 1 is not an object.
If the user, instead, right-clicks on the Edit link and opens in a new tab (instead of a popup), the buttons are shown. Hope that helps.