HTTPS Monitor / Send String containing question mark "?" not working -> turned into space

Hi,

 

today we ran into a problem, where a HTTPS monitor is not working properly.

 

The send string looks like this:

 

GET /abc/def/service?sdl HTTP/1.1\r\nHost: abc.com\r\nConnection: Close\r\n\r\n

 

Unfortunately, the server returns a 404. In the monitor log I can see that the string is properly sent, but on IIS side it seems that the '?' is turned into a space.

 

If I try a curl from F5 like this:

 

"curl -vk https://10.1.1.1/abc/def/service?sdl"; - it works properly.

 

If I curl to .../service%20sdl, I receive also a 404, so I assume that somehow the question mark is not forwarded properly, but changed to a space.

 

We are running v13.1.0.7. I saw some articles on AskF5 that stated, that you need a "\?" starting with v10.20, but it should only affect old versions and the article was archived.

 

Any other ideas?