SharePoint Versioning Enabled Yet not Working

As far as I am aware, there have not been made any changes to our versioning on SharePoint Online. Yet out of a sudden, changes in files or uploads of equally named files with differing content do not lead to new minor versions anymore. Besides numerous tests, the only remediation I tried was to set versioning off and on again. However, that did not help. Is there any setting I am not aware of? Could you guys please help us out? Thank you very much in advance for any help!