Auto updater download failure - install4j

Question

We have configured an auto-updater to our service using the ‘updater-with-silent-version-check’ and using the unattended mode.
When we invoked the Updater.exe, it failed with the below error. When we invoked it again, it successfully downloaded the new version from the same URL and upgraded to next version.
What could be the probable reason for the earlier failure?
we passed the URL to the Updater as an argument : -VpatchAgentUpdatesUrl=https://xxxx.company.com:8443/updater-service/updates.xml
[ERROR] com.install4j.runtime.beans.actions.update.CheckForUpdateAction [ID 190]: could not download file
java.net.MalformedURLException: no protocol:
java.net.MalformedURLException: no protocol:
at java.net.URL.<init>(Unknown Source)
at java.net.URL.<init>(Unknown Source)
at java.net.URL.<init>(Unknown Source)
at com.install4j.runtime.installer.helper.content.HttpRequestHandler.connect(HttpRequestHandler.java:120)
at com.install4j.runtime.installer.helper.content.Downloader.connect(Downloader.java:152)
at com.install4j.runtime.installer.helper.content.Downloader.connect(Downloader.java:25)
at com.install4j.runtime.installer.helper.content.HttpRequestHandler.connect(HttpRequestHandler.java:116)
----Update-----
We are passing the updater URL through command line argument to the Updater.exe.
We did the below changes.
1) In the Installer -> Auto-update options, 'URL for updates.xml' option is set to empty.
2) In the Installer -> Screens & Actions -> 'Updater with silent version check' , defined an installer variable 'updatesUrl' with value as ${compiler:sys.updatesUrl}
3) In the Installer -> Screens & Actions -> 'Updater with silent version check' -> Start up -> Check for Update -> set the 'Update Description Url' as ${installer:updatesUrl}
4) Invoking the Updater.exe with option -VupdatesUrl=https://xxxx.company.com/updater-service/updates.xml
Sometimes it’s working fine with the proper URL and sometimes its failed and URL field is shown as empty in the updater log.
Below is the properties shown in the updater log in the error case.
[INFO] com.install4j.runtime.beans.actions.update.CheckForUpdateAction [ID 190]: Execute action
Property variable: updateDescriptor
Property showError: true
Property rollbackSupported: false
Property connectTimeout: 10000
Property readTimeout: 20000
Property url:
Property askForProxy: true
Property acceptAllCertificates: false
Property connectionFailureScript: null
Property requestHeaders: []