Taking an extreme approach. Try installing 4.21 now. Might as well use the newest release. Install in a new directory not the default one.
Then create a modified shortcut and run DT with --configdir parameter so --configdir “path” where path is a new blank folder of your choice to house the config files. This is a clean unrelated install with all defaults… how does this work??
Certainly not. But “this application got slow” tells us nothing, and you seem like you’ve already given up trying to figure our what is wrong.
If you don’t want to figure out what is wrong there is nothing we can do to help you.
I am not angry one bit, what gave that impression?
“This kind of reply are really depressing” Why are you depressed? 
I too am a developer, and I welcome feedback anytime.
Cheers!
I didn’t experience any slow performance issues, I’d consider that a separate issue.
I think one way or another DT needs to implement a genuinely clean install/uninstall, It was really only after these steps that everything cleared up:
Uninstall DT
Remove or rename: C:\Program Files\darktable
Remove or rename: C:\Users\(username)\AppData\Local\darktable
Remove or rename: C:\Users\(username)\AppData\Local\Microsoft\Windows\INetCache\darktable
Re-boot, Re-install DT
Some custom settings may be lost, but that might be OK because I noticed some changes once things were cleaned up that i wouldn’t have noticed otherwise, it seems certain things could persist for a long period without the user being aware, even if only one or two steps above is done but not all - if you’re not sure just rename folders instead of deleting.
Doing these on windows as part of an uninstall is considered bad form. Those are user generated files that contain user generated information and they are not recoverable if removed.
Then clean install or clean uninstall options need to be presented.
Do you still have your original darktablerc file from appdata?
I’ve seen multiple report like yours and I’ve tried to understand what’s going on. Ive asked for someone to share the files but so far no volunteers.
Its documented so people can choose to remove it or not. I’m not sure why people the uninstall/reinstall paradigm does any good.
Is this the before? The after? I would like both.
OP, sorry for the kinda off topic.
that’s the old one before fixing the issue
Can you send the current?
These are difference:
cache_memory=536870912
host_memory_limit=16347
ui/style/preview_size=250
Plus OpenCL ones that we should not be using anymore
I’m going to add the host_memory_limit to my windows build to see if it causes an issue. Can you try the same to see if your issue returns?
Does darktable use ImageMagick? That’s the only program I know that uses the name “Magick”.
Yes, it uses it to convert any format it doesn’t understand natively. Either imagemagick or graphicsmagick, either works
Okay. magick should never crash with an access violation, of course. Is there a log entry that says what magick command was attempted?
What version of ImageMagick was used? “magick -version” will say.
If the problem is reproducible outside darktable, ie at the command line, then I expect that is fixable by the ImageMagick people if it is reported at Issues · ImageMagick/ImageMagick · GitHub
Possible workarounds: upgrade to a current version of ImageMagick, or remove ImageMagick and let GraphicsMagick do the work.
That’s because I used the application for work, my clients expect results rather quickly. You guys seem to be judgemental and make assumptions about my reactions, not upcommon in forums I’ve noticed, unfortunately.
It’s fine though. I’ll wait for a future software release and test it. No hard feelings I hope, and have a great day!
You say you’re a software developer, you know that’s not how problems get fixed.
if you’re a developer as you wrote before you’ll obviously know, that issues usually aren’t solved by magic. So you might just wait and pray, but since no developer ist on windows i doubt, just a diagnosis of symptoms will help.
Bite the bullet, try to play with different opencl settings, make use of the debug output options if started from command line and provide valuable hints to help the developers to help…
Of course this needs time, but why should a developer spend his spare time to solve an issue that’s not worth that you spend time to help to find a reason…