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Sounds like it wasnt put back together too well. Was it honed or sleeved? Was a new rubber seal kit installed? It will be the rear rubber seal inside the master around the pushrod that is leaking. Master needs to come back off to fix it. Hope this helps. Please keep us updated as to your progress. <Edit> The seal/s in question are not around the pushrod; I wasnt thinking straight when I typed the reply. The seal around the pushrod at the rear is a dust boot, the seals that would be leaking are inside the bore of the master cylinder.

Given you paid to have it restored (which I assume was the bore only because the outside looks unrestored), I’d take it back, tell them what’s happened, and see what they say. Worst case, they don’t accept any responsibility, and you either have to pay them again / more, take it somewhere else, or do it yourself. But, at least it gives a chance they might fix it under some sort of warranty, or provide some explanation that might help decide the way forward. It would cost nothing to take back to see what they say…so nothing to loose, really.