This documentation page may help you find the issue. Furthermore, you can set the REST publish node to trace, to see why Mendix is choosing the operation.
Alright, seems like I solved it. Some wizard must have put a spell on my rest calls, cause I have 2 more Patch calls (operations) in the same resource with URL's: “URL/resource/path1” and “URL/resource/path/param1/param2” and I used to use “URL/resource/path2” for my non-functioning Patch call. I then tried “URL/resource/path2/param1” and “URL/resource/path2/path3” which also didn't work. I now have “URL/resource/path2/path3/path4” which does seem to work for some reason.
In short: Apparently my URL just needed a few more operation paths in it's URL to make it work and not suggest me using a GET call anymore. I've got no idea why or how, so if anyone has a better understanding of why this happend, please let me know, I'm very curious.
To resolve error method 405 not allowed can be solved through different methods Paslechoix. You can do it by completing restoring your website from a backup. This can be done by going to hPanel, and choose Backups under Files. Now tap the option of Select from Files backups and choose the date tap on Show files, which will load all your content from that date. Then you can navigate through the folders and choose the ones that you need to restore before you are about to press on Restore files. In the end, press on the option of Restore again, and the system will begin the process and send an alert once the process is finished. This will surely resolve the 405 errors code easily.