Hi @Ioannis5EEA - Thanks for submitting your bug report. We need a few more details to try to help with the issue.
Are these new projects or upgraded projects?
In Settings > Audio Do you have "Generate waveforms automatically during import" checked in the settings?
If you highlight the media in your project panel and then navigate to the clip menu and select "Generate Audio Waveform" does that help?
Do you have your media cache settings set to custom?
Sorry for the frustration.