Hey I managed to reproduce this issue multiple times and now I found the solution to prevent this from happening. Recently I played in Energritz's server and trying to build building that looks exactly like my Traditional Japanese House  with blueprint. I tried 3 times, and all of them end up being "Someone else is using that", then finally after that I tried once more, but I don't open the blueprint station and wait 3-5 minutes(until the transparent layout of the building pop up) then when transparent layout already pop up, I click the blueprint station and wallaa I can put required materials. So don't click/open the blueprint station and wait until that transparent building layout loaded (possibly you still uploading your blueprint to the server). Hopes it helps. Happy blueprinting!   
"Old picture when I was so frustrate from this issue and want to report, but then I tried once more.. "
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