Multicam Lag making my life HARD!!!!!!

Hello all,
I've just about had it with this problem! 
I'm a wedding video shooter and editor.
I have a good computer , with the
nvidia GEFORCE 3060 Rtx
Intel(R) Core(TM) i9-9900KF CPU @ 3.60GHz 3.60 GHz
64 GB RAM
cache - program- project files split to 3 diffrent drives.

One of my sequences is a 2 cam dance seq that is usually about 30-40 min long. That multi cam is fine.
After that i want to take that multicam that is already jumping between cameras, and multi cam it by itself.
For example.

Take the multicam from minutes 00:00 - 10:00
and take the same multicam from 10:00 - 20:00

and jump between times and multicam it  
( I HOPE IM MAKING SENSE)

But the multicam is sooo laggy!! Even with proxy, even with low res playback.
I used to do it all the time., now its just to bad!

Please please please help me!
Thanks all