Problems with self signed and let's encrypt certificate

Where are building an application but the backend of this application normally will run w/o proper certificate (is a thin client for our main software). Sadly every production build are unable to establish connection to said backed. We also tried with a let’s encrypt certificate without any luck.
We are building our app with this ( following are your guide

ionic cordova build android --prod --release

we also edited our /platforms/android/AndroidManifest.xml and added the debuggable flag
and even edited platforms/android/CordovaLib/src/org/apache/cordova/ so the webview can ingnore certificate errors