Power BI Service semantic model refresh sudden performance loss

We've had several semantic models go from < 5 minute refreshes to > 1 hour in the last 3 days.

I've tested various things, but it boiled down to an unexplainable result:

I can publish an exact copy of the model to the same workspace and it will refresh as normal, even while the original is spinning for an hour. This alone seems to prove all connections and data sources within the model are fine. In Desktop, works as normal, including the original.

Why does creating a new model Id fix it? How can I make orignal model to perform the same as the copy?

Started a thread in the forums and 2 other users are experiencing the same.