I have a noninformed thought on this... I think a lot of these issues are actually because they're not on modern Cloud yet.

I think GitHub was rolling everything themselves when Microsoft bought them. Ever since, MS has been working to strategically shift to Azure but that's a difficult and careful process that takes time.

In the meantime, the AI boom hit and usage went through the roof, crippling aging non-scaled infrastructure that hasn't had a chance to be modernized yet.

A lot of issues might very well be "we broke something while migrating", but I think a lot are also simply capacity issues on legacy.