As mentioned above, I have also been experiencing a long standing 2nd freeze that occurs when I navigate via Drives & Devices to a folder with files that have not yet been imported into MC. The freeze occurs maybe 25-50% of the time that unimported files are first touched. Once MC resumes from this freeze it never occurs again on that batch of files. Only when I navigate to a different folder with unimported files does the freeze reoccur.
I suspect that this is not a freeze, but it can certainly be made into a freeze, or even a crash. I just crashed MC by pushing it around too much. Sadly, I didn't have logging turned on.
Just to confirm though, you are talking about the Explorer function under Drives & Devices in MC, correct?
When you open Explorer be very aware of the options at the top, because they have a large effect on how Explorer works. For example, if you select a Mode of "All Files" and tick the "Show Files In Subfolders" box, MC will read every file in the directory or drive you have selected, and
import them all into a temporary database in its Library. All files!
Typically, MC shows the "Working" message in Explorer, but it isn't obvious how hard it is working. Windows Task Manager doesn't always assign much disk activity to MC, as MC offloads that work to Windows, so the activity is shown mostly under "System" using Windows Resource Monitor. [I just caused a freeze in Windows Resource Monitor while thrashing Explorer!
] But some of the time Task manager will show a disk is being thrashed, because Explorer reads every file, and every tag in those files, in order to import them temporarily and show the files and their tags in Explorer.
Explorer is very handy. It can even temporarily import files, show you the tags, and allow you to update those tags, but never have the file imported into the MC Main database. Neat.
But it must be used with care. If Explorer says it is "Working" you pretty much can't do anything else on the Explorer tab in MC, other than wait. If you click on anything else in the MC Explorer interface, you are likely to see a freeze. If you keep clicking around, and a lot of files are being processed, you are likely to see a crash. You can scroll around the Tree, and go to another tab, and do things. But not click on another folder in the Explorer tab, for example.
Maybe this could be improved. But when you are loading a drive at 100%, you really just have to wait.
Note that the temporary database does get purged between MC runs, I believe.
EDIT: Confirmed. Purged when MC is restarted. So while you can go back and look at a folder and its sub-folders without a second wait, if you close MC and try again, you will have to wait again.
You can set up a View to show what is in the Explorer Database. The rule for file display is just "Limit database to: Explorer", or "~d=e" in short form.
I just loaded a folder which contains 412 sub-folder, 72,680 files, and 653Gb of data, mostly images, video files and Premiere Pro projects. I didn't time it, but I think it took Explorer about 15 minutes to finish working. Oh, Explorer builds thumbnails as well. Thumbnails for 71,389 jpg images from Time Lapse video creation. Also, it seems I had Audio Analysis turned on for videos, which I normally do, and Explorer used that setting. That adds some load and time.
To avoid all of the above, and still be able to use Explorer and drill down to a folder you want to look at, select a Mode of "All Files" and leave the "Show Files In Subfolders" box unticked. When you get to where you want to be in the drive structure, tick the box to view all fils below that level. Or change the Mode to a setting that suits your activity.