Hello, so I am in a very unique situation and need some help.

I am editing a large project on an older version of Final Cut Pro (6). I know, I know, I should upgrade. I made sure to convert all my video files to Apple ProRes 422. Everything was going great until one day after turning off my old mac for a few days, I opened up my project and found that it could no longer play my project. Everything feels extremely laggy, and it only plays for a few seconds before dropping frames.

I don't know what changed in that time. I know I'm stressing my system somewhat with how much video I'm working with, but I was editing just fine for a long time. So I know my computer is capable of handling this much video; I think there is a setting that I must have wrong somewhere.

All my footage is stored on a 7.28TB Lacie hard drive. So is my project file and scratch disks (I hope that's all right?)
There are currently 888 gigabytes free on this external lacie drive. I don't think this is the issue because I remember this number going down to around 750 gigs free, and the project slowed down a bit but still played fine. I agree I could be wrong on this though.

My computer is an old mac (can get you the specific specs if you need it)

My footage is 23.98 fps
1920 x 1080
13.6mb/sec data rate

My sequence settings are also using prores 422 as the compressor.

For system settings, my RT setting is on safe. My video quality setting is on low.

My Final Cut project file is 11 mbs.

I have tried trashing preferences, and it now gives me a message saying "One or more frames was dropped during playback. It gives me some ideas on how to fix, like lowering compression data rate. Also in red, it tells me that RT Extreme has determined these dropped frames were caused by slow disks. I can elaborate here if needed.

Let me know what else I can share that would help. I would super appreciate any ideas on what's causing this huge change, whereas for weeks I was playing and editing with this large project just fine.