Front master cylinder leaking

Hi folks!

Took the strada in for a master cylinder replacement late last year, as it was leaking and it was done under warrantee. It's since started leaking again. Has anyone had this? And does anyone know if work done under warrantee carries outside of the warrantee period, or have I got no comeback now?

Cheers and hope you're making the most of the sunshine this weekend!

Sorry for the delay, not getting notifications these days. It's the seal between the main reservoir and the cap. The whole unit was supposed to have been changed under warrantee last time so it's a little weird.