Some eclipse packages are split across multiple bundles. The maven-bundle-plugin, by default, will put in a package import, which could get connected to only one of the bundles. If that bundle doesn't have the class, you get a classnotfound exception. Which bundle gets wired is arbitrary - often differing based on platform, build, etc.
The fix is to identify all the split packages in Eclipse (these can be found by opening the Eclipse HELP and searching using the keywords ( split packages map )). Then for each split package, add a Require-Bundle for each bundle that has some of the classes for that package.
Add the Require-Package directive to the affected POMs to make these stable against possibly wrong wiring.