FCP7 on Yosemite: A/V sync trouble

[Le bricoleur]

First thing, I'm sorry for my English, it's really awful. I'll try to do my best.

I'm a video editor.
I recently had to buy a new iMac 27inch (OS X Yosemite 10.10.2 - 3,5 GHz Intel Core i7 - RAM 16 GB - NVIDIA GeForce GTX 780M 4096MB).
Usually I work on FCP7, but on this new machine I have encountered an unusual problem when I try to do A/V sync.
If i put in sync audio and video "on the clapperboard", at the beginning of the clip, in the space of a few minutes the clip go out of sync, considerably.
With Premiere Pro (using same clips, audio and video) I don't have this problem. And, obviously, this problem does not exists on my old Mac with old OS.

Why?
Someone can help me?

 

[boch82]

First thing, I'm sorry for my English, it's really awful. I'll try to do my best.

I'm a video editor.
I recently had to buy a new iMac 27inch (OS X Yosemite 10.10.2 - 3,5 GHz Intel Core i7 - RAM 16 GB - NVIDIA GeForce GTX 780M 4096MB).
Usually I work on FCP7, but on this new machine I have encountered an unusual problem when I try to do A/V sync.
If i put in sync audio and video "on the clapperboard", at the beginning of the clip, in the space of a few minutes the clip go out of sync, considerably.
With Premiere Pro (using same clips, audio and video) I don't have this problem. And, obviously, this problem does not exists on my old Mac with old OS.

Why?
Someone can help me?

Similar issue...its something with the playback...usually if you hit play, stop and play again it will play in sync.

I only use FCP 7 when getting things from vendors that we hire. We have migrated the whole office to PP for all internal projects.