My FCP7 + Yosemite broke on the last update, if you do a search on here you’ll see many people have problems but there are some who don’t. You’re talking about very old software with no updates over the past few years, if you rely on it for work – don’t do it or download FCPX. My solution (with a MacPro) was to use 2 drives, 1 with 10.8 and FCP7 that never misses a beat and the second with Yosemite and all other programs, a 3rd drive has Yosemite and FCPX.
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