Hi,
I'll try to release v4.0.1 soon, essentially to fix annoying false-negatives and to include recently-updated localized messages.
I'm thinking notably of tackling:
- a warning raised for re-declaration of the "rendition" prefix
  
https://github.com/IDPF/epubcheck/issues/585
- reporting of font types which are not Core Media Types
  
https://github.com/IDPF/epubcheck/issues/586
- localization updates
  
https://github.com/IDPF/epubcheck/issues/590
If you have any critical bug to report and you'd like included in this bugfix release, or localization you'd like to contribute, now is the time to speak out! Please let me know in the next 7 days, i.e. before October 7.
Romain.