Aria2 WebUI: Secure Connection not working

Hello forum,
I installed the download-manager aria2 and its luci-frontend webui-aria2 to manage the downloads. However, the frontend can't connect to the aria2-program because of security-problems. The connection seems to use ssl.
There is a thread on github about this but their solution didn't help. I also tried the LEDE-wiki-page about ssl-problems but I still don't get a connection.

What I did is this:
I created a certificate, a private key, a signing request, and a signed certificate on LEDE. I then configured luci to use them for ssl and added a security exception in my firefox (as mentioned in the wiki). I used the same keys/certificates for aria2-webui. Luci can make SSL without problems now. But aria2-webui still has problems. When I hit F12-key in firefox, the console shows me things like this:

"192.168.0.111" rpc.js:23
Array [ Object, Object, Object, Object ] rpc.js:42
"pascalprecht.translate.$translateSanitization: No sanitization strategy has been configured. This can have serious security implications.[...] angular.js:13424
"Syscall is initializing to" Object { host: "192.168.0.111", path: "/jsonrpc", port: 6800, encrypt: false, auth: Object, directURL: "" } syscall.js:22
"not using websocket for aria2 rpc due to: " DOMException [SecurityError: "The operation is insecure."
code: 18

...and...

"jsonrpc disconnect!!!" jsoncall.js:46
"calling json rpc" syscall.js:48
"jsonrpc disconnect!!!" jsoncall.js:46
"calling json rpc" syscall.js:48
"jsonrpc disconnect!!!" jsoncall.js:46
"calling json rpc" syscall.js:48
"jsonrpc disconnect!!!"
The webui-page then is a page with "mixed content" and can't connect to aria2.

I now wonder if aria2 needs a different certificate than luci because the wiki reads:

"What is extremely important is the value for CN (common name), DNS.1, and IP.1."

These values (in /etc/ssl/myconfig.conf) are set to 192.168.0.111 in my case, which is the routers address in my home-LAN. However, aria2's webui has the address: 192.168.0.111/webui-aria2/.

Do I need a different certificate for this?

I am using LEDE Reboot 17.01.1 r3316-7eb58cf109.

More than two years, this issue still exist, is there any solution?