Duplicate Excellent Workbench Blueprint

I received the blueprint for the Excellent workbench as part of the main plot. It is still available for purchase through the watch merchants and later merchants for 100 tier 4 essence, even though I have it. Every other blueprint greys out after I acquire it, so I am assuming this is a bug.

Due to inconsistent internet connection, I mostly play offline. I have not progressed far enough in Online mode to verify this bug there as well.