Hi @Balazs_Nemeth , and welcome for the community!
This problem is likely not because of encoding. If so, caching would just skip that one file, assuming that the contents of the file is different from the cache contents.
This problem is likely caused by the SonarSecurity plugin. We had an internal bug report (so I can’t share the links) with the same symptoms: 0 out of n files cached. It turned out that the plugin, which injects its own rules into the SonarJava plugin, requested the unnecessary reparsing of source code files under specific circumstances. This, effectively, disables caching for the whole SonarJava plugin.
We have a ticket about this: SONARSEC-3439.