I've found another odd behavior in Pro that's cropped up recently. When running geoprocessing tools, they will occasionally sit there with a status of "Running..." after it reports "Succeeded at Tuesday, June 19...", with the progress bar just scrolling through like it's still working.
The ArcGIS Pro GUI becomes incredibly slow, and Resource Monitor reports higher than normal usage (at least 25% on a quad-core machine, when normally it only uses 5-10% just sitting there). There does not appear to be any abnormal disk, memory, or network activity. The ArcGIS Pro Diagnostic Monitor doesn't report anything out of the ordinary.
The system will sit here as long as you let it. Most of the time I can clear it out by switching from the map tab to the Catalog tab in the main window, but sometimes a hard Resource Monitor => End Process is required to break it out of its slumber.
I've experienced this when working on local datasets in a project saved locally. I'm not aware of anything that would be relying on the network (as that's been a problem for us in the past with our setup). I am also not writing the results to XML, as per Dan's answer here. I'm running ArcGIS Pro 2.1.3 on Windows 10 Pro, Version 1803 (the April Update)
Anyone got any ideas?