[Transient] Merge button sometimes not appear in merge widget

Summary

Sometimes we observed in different E2E tests that the Merge button was missing causing the test to fail.

Example failed tests: #364604 (closed), #364421 (closed), #363724 (closed)

Steps to reproduce

Since it's a transient behavior, it's quite difficult to reproduce. But looking at the failures mentioned above, it has been happening from time to time.

What is the current bug behavior?

Visiting a merge request page, page looks completely rendered but no merge button in the merge widget.

What is the expected correct behavior?

The merge button to be visible in the merge widget

Relevant logs and/or screenshots

From one of the failure example above

Output of checks

Seen on Staging.gitlab.com

Possible fixes