It took me almost a month to install thunderbolt display firmware update 1.2 on OSX Yosemite.
The update just failed every time I tried to install. Even more annoying, it miraculously reappeared in the updates a couple of days after the botched install.
My MacBook was connected to my Thunderbolt display with its shell closed. All I had to do is to open the shell and the update installed just fine.
Doing what Apple suggest here just wasted time.
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