Sandboxing QtWebengine for apple store - qt

Question

For the last 4 days I've been trying to publish my app in the apple store (which I've never done before). In it I use qt 5.12.1 with qtwebengine. But I really got stuck with sandboxing webengine because after sandboxing app won't even start. I followed this https://mediaarea.net/blog/2018/02/14/QtWebEngine-MacAppStore initially without recompiling and changing webengine but afterwards doing this as well (Unsuccessfully though 'cause they used qt 5.9). I tried as well suggestions from this thread https://forum.qt.io/topic/102212/qtwebengine-signing-issues/4 but had no luck. So I thought maybe you guys could give me some tips on how could I do this. Here's my script for signing package.
echo SIGN PACKAGE
# special case for QtWebEngineCore
find dist/MyApp.app -name Info.plist -exec plutil -replace CFBundleIdentifier -string "com.MyApp.desktop" {} \;
find dist/MyApp.app -name _CodeSignature -exec rm -fr {} \;
find dist/MyApp.app -name "*.dSYM" -exec rm -fr {} \;
# 1*
for f in $(find dist/MyApp.app/Contents/Frameworks -name '*.framework' -type d)
do
codesign --force --verbose -s "3rd Party Mac Developer Application: MyApp (*)" $f
done
for f in $(find dist/MyApp.app/Contents -name '*.dylib' -type f)
do
codesign --force --verbose -s "3rd Party Mac Developer Application: MyApp (*)" $f
done
codesign --entitlements app/MyApp.entitlements -s "3rd Party Mac Developer Application: MyApp (*)" dist/MyApp.app/Contents/MacOS/MyAppUpdater
codesign --entitlements app/MyApp.entitlements -s "3rd Party Mac Developer Application: MyApp (*)" dist/MyApp.app/Contents/MacOS/crashpad_handler
# 2*
codesign --force --verify --verbose -s "3rd Party Mac Developer Application: MyApp (*)" --entitlements app/MyApp.entitlements dist/MyApp.app
codesign --force --verify --verbose --sign "3rd Party Mac Developer Application: MyApp (*)" --identifier "com.MyApp.desktop" --entitlements app/webengine.entitlements dist/MyApp.app/Contents/Frameworks/QtWebEngineCore.framework/Helpers/QtWebEngineProcess.app
# 3*
codesign --entitlements app/MyApp.entitlements -s "3rd Party Mac Developer Application: MyApp (*)" dist/MyApp.app/Contents/MacOS/MyApp
It is kinda mixture of all suggestions of those posts. Eventually I managed to get rid of all apple errors except of this one.
ITMS-90296: App sandbox not enabled - The following executables must include the "com.apple.security.app-sandbox" entitlement with a Boolean value of true in the entitlements property list: [( "com.MyApp.desktop.pkg/Payload/MyApp.app/Contents/MacOS/MyApp" )] Refer to App Sandbox page at https://developer.apple.com/devcenter/mac/app-sandbox/ for more information on sandboxing your app.
The problem with it is if I move part where I sign webengine to (1*) I'll get my app through apple checks but it will crash. But if I leave it where it is right now I will receive error above. I had initially 3* above 2* and tried the combination of moving around webengine signature.
For more details I will attach my MyApp.plist, MyApp.entitlements and webengine.entitlements below.
I run macos mojave 10.14.3 on VirtualBox, qt 5.12.1
webengine.entitlements
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>com.apple.security.inherit</key>
<true/>
<key>com.apple.security.app-sandbox</key>
<true/>
<key>com.apple.security.cs.disable-executable-page-protection</key>
<true/>
</dict>
</plist>
MyApp.plist
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>CFBundleDisplayName</key>
<string>MyApp</string>
<key>CFBundleExecutable</key>
<string>MyApp</string>
<key>CFBundleIdentifier</key>
<string>com.MyApp.desktop</string>
<key>CFBundleSpokenName</key>
<string>MyApp</string>
<key>CFBundleGetInfoString</key>
<string>blalba</string>
<key>CFBundleIconFile</key>
<string>MyApp.icns</string>
<key>CFBundlePackageType</key>
<string>APPL</string>
<key>LSMinimumSystemVersion</key>
<string>10.11</string>
<key>NSPrincipalClass</key>
<string>NSApplication</string>
<key>NSMicrophoneUsageDescription</key>
<string>Microphone is required for voice messages and calls</string>
<key>NSSupportsAutomaticGraphicsSwitching</key>
<false/>
<key>CFBundleVersion</key>
<string>0.5.1225</string>
<key>CFBundleShortVersionString</key>
<string>0.5.1225</string>
<key>LSApplicationCategoryType</key>
<string>public.app-category.social-networking</string>
<key>NSHighResolutionCapable</key>
<true/>
</dict>
</plist>
MyApp.entitlements
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>com.apple.security.inherit</key>
<true/>
<key>com.apple.security.app-sandbox</key>
<true/>
</dict>
</plist>
I ran out of ideas and information of how to solve this problem. One more problem is that I've never published app in apple store before and I don't usually develop under macos as well. So everything is new to me(love it). And if I don't do this my team lead is going to hang me if I don't do this myself first.
So any help appreciated.