You should review your modsecurity rules. I’d try first without modsecurity at all if the client works properly. I’m not sure if there is an official rule set, I found two links to virtual machines where it seems to be used:
I was able to disable a specific ModSecurity Rule on my hosted server, and for now it seems to be a solution.
Apparently it is the forceRequestBodyVariable Rule with ID 960904.
It could be that my webhoster is very strict with security rules, but maybe this is also an opportunity to change the desktop client to not violate against this issue?
Usually such a rule set comes with some default settings which might or might not be suitable for a specific application. I don’t know enough of the client-server communication to tell if this behaviour is required and the rule must be disabled.
I’m having a great deal of fails like mentioned by pato, but since I’m using a hosting service I’m not able to install, well, virtually anything.
So modsecurity is not a way to go for me.
My win10 client is failing to PUT many files into my cloud. PDfs, Mp4, Zip, PcbDoc, php.
Apparently not any particular file type. Many are small (in case you’re thinking about large file size issues).