FCPX 10.1 Very slow on iMac and lots of spinning beach balls

You don't have to optimize, but if you import properly you won't be using .mts files but QuickTime, which is incredibly more efficient for production.

I haven't seen this problem in 10.1.4 using long .mts files. It hasn't crashed, since I can't remember when, certainly not this year, and I use it every day. There was almost no change in the FCP application in 10.1.4 with the exception of new codec integration which was added with the Pro Video update, not the application update. The update was so small that 10.1.3 can open libraries created in 10.1.4.

I'm thinking something else has changed on your system that's causing this problem with FCP, maybe some plugin or some other software that interacts with FCP.

Thanks,

Any suggestions what plugins should i look after on which soft might interact with FCP?

Lemo

AAny plugins might do it. Audio plugins seem more prone to problems, but that's just that they're reported more often. Do you have any plugins? Try removing them all to start.

This issue persists on the latest OS X 10.11.5 and 10.2.3 FCP X. In an attempt to narrow down this issue, would it so happen that everyone experiencing this is running a secondary display? Also do all of you have fxFactory plugins?

At this point in time I believe you should start a new thread and give specific information about your issues, including your hardware setup.

This thread is very old, and FCP X works just fine for most people today, as it did back then. If you have been suffering from performance issues all this time, there is likely something else, specific to your setup, that is involved, and not a yet-to-be-fixed bug. If you keep waiting for a new release to solve those issues, you are likely to be perpetually disappointed.