When creating/updating an item with an asset field, the assets modal always has a higher z-index than the upload asset modal, which should be higher.
The problem with this is, when you go to select and upload an asset, the upload modal appears below the current modal - hidden. You would need to close the current asset selection modal to see the asset uploader modal, and then close that once you’re done uploading and finally open the selector back up and select the asset you uploaded. I also see that when changing the z-index of the uploader modal to always be on top, the selector modal adds 1 to that to always be on top - so I cannot fix this using CSS.
This was not the case before, it would simply go like this: click to select asset, click to upload asset, upload asset, select uploaded asset. Now it is: click to select asset, click to upload asset, close modal, upload asset, close modal, select uploaded asset.