Solved
AEM Cloud manager - Builds fail on Stage when content package included, but works on Dev environment
Having similar issue to this https://experienceleaguecommunities.adobe.com/t5/adobe-experience-manager/cloud-manager-deployment-content-package-not-getting-deployed/m-p/411723
We need to integrate Phrase for our site translations. And have configured as instructed by Phrase here https://support.phrase.com/hc/en-us/articles/5709667773084-Adobe-Experience-Manager-AEM-TMS- (Open section > AEM as a cloud service)
1. in /pom.xml
<memsource.version>3.1.15.5</memsource.version>
..
<repositories>
<!-- for Phrase Memsource -->
<repository>
<id>phrase-memsource</id>
<name>memsource</name>
<url>file:${project.basedir}/repository</url>
</repository>
</repositories>
2. in /all/pom.xml
<dependency>
<groupId>com.memsource</groupId>
<artifactId>aem-memsource-plugin.all</artifactId>
<version>${memsource.version}</version>
<type>zip</type>
</dependency>
--and copied "repository" folder (/all/repository) that contains the memsource zip file.

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The same setup, SUCCEEDs on DEV builds, but FAILS on STAGE build.
Failed on stage:
Logs show this error on STAGE:
[91mjava.io.IOException: Error while loading package /tmp/cp2fm-converter4471812595875810708/sub-content-packages/aem-memsource-plugin.all-3.1.15.5.zip
[91m at org.apache.jackrabbit.vault.packaging.impl.ZipVaultPackage.<init>(ZipVaultPackage.java:81)