I’m running KiCad 8.0.3 on Windows. Everything seems to work great with one odd exception. When I first open a project, I usually get a KiCad Error dialog saying, “File: [filename].kicad_prolck couldn’t be removed (error 0: The operation completed successfully.)” After I click away that error dialog, KiCad runs just fine. Rarely (it seems), KiCad opens a project without throwing that error, but when I’ve tried to troubleshoot that situation, KiCad has always gone back to its behavior of showing the error message about “… kicad_prolck couldn’t be removed (error 0: The operation completed successfully.)” Perhaps this is just a small nuisance error and can be safely ignored. I would welcome feedback.
Close Kicad. Open each project with windows file manager and delete any *.lck files you find.
Projects should then reopen with Kicad correctly.
lck files are usually created if Kicad is not closed correctly. eg. a crash.
If it keeps occuring alot, you can make a simple python script to scan and remove these files in subfolders for you. I use similar script to keep deleting those cache files from my dropbox folder.
I am going to add the deletion of these lock files as well. They don’t work well with dropbox… or dropbox does not work well with it 
Bas
I’ve tried your suggestion several times. The problem persists — KiCad still reports the error that I described.
A bit more info, but it doesn’t seem helpful: I confirmed with Windows Explorer that a ‘lck’ file did not exist in a couple of my project folders. However, when I opened KiCad and then opened either of those two projects, I got the same error both times … File ‘_____.kicad_pro.lck’ couldn’t be removed (error 0: The operation completed successfully.). I then tried Closing the project then Open Recent (the same project), and I got the error every time … on both projects that I tested. It certainly seems strange that KiCad is reporting that it can’t remove a file that isn’t there.
May not be your problem but, I had the same/similar trouble last year and discovered it was a ‘Plugin’ that was causing it.
When I removed the Plugin, no more problems. When put the Plugin back, problem started again. It was an easy fix…
Thanks for the info, but, in my case, my KiCad has no plugins installed.
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I previously asked for help on this topic but that thread was closed after 90 days so I can’t post there. However, I found the problem and I’ll describe it here in case others might benefit from this info. The problem was (still is) that KiCad reports, on opening a project, that it cannot remove the ;___kicad_pro.lck’ file. The full error message looks this this: “File ‘------.kicad_pro.lck’ couldn’t be removed (error 32: The process cannot access the file because it is being used by another process.)”. I’ve discovered that the problem occurs when using KiCad while Dropbox is running in the background. KiCad apparently sees that Dropbox is another process that’s holding the ‘.lck’ file “OPEN”. That file isn’t exactly OPEN but I suppose Dropbox makes it appear that way to KiCad, so KiCad reports error 32. If you don’t want to see that KiCad error, just momentarily suspend Dropbox’s background “sync” operation.
Merged followup post and opened topic
I’m not a dropbox or windows user but surely the solution would be to tell dropbox to ignore lock files for syncing, if possible?
I quote fromDropbox forum:
Excluding file extensions from being synced is currently not possible.
This is a royal Payne alright. Suffering from this for years.
The one thing I can think off is to make a python script (or let chatgpt do it for you, this it can) and let the script auto run every minute or so. And of course let it start upon booting.
You can also include those space consuming cache file as well when you are at it.
Kind regards,
Bas