MacBook Pro M4 really struggling with Node render

Ok, ive not been using Resolve for long, so im going to assume this is user error, but I cant see where im going wrong.
Im on a M4 pro MBP with 24GB, using the final release of DR20. Mac Os15.5
I have a 3.5min long 4k canon clog3 clip, and I keep trying to use the noise reduction on my second node, after a CST. Ive turned on Node cache and it took about 20-30mins to render the NR. The blue line went across really slowly but it got there. Then I had smooth playback. I can adjust nodes further down the chain without any issues. I saved the project a few days ago and have just gone back to it. The best I can get is about 12fps playback at half resolution. Full resolution (1080p timeline) drops to 1-3fps. This is totally unusable. The thing I cant figure out is why. The node cache is on, and the cache manager is showing a big file, so it's still cached, only it's not. Render cache is switched to user, but nothing is getting rendered. The number on the Node is now red again, but it's not re rendering anything.
What am I missing? This isn't the first time ive had to waste yet more time letting this node re render (had to do it about 4 times on the first day, as it kept re rendering. Nothing has been touched in the first node, and no cuts or edits done to the single clip.
Im on a M4 pro MBP with 24GB, using the final release of DR20. Mac Os15.5
I have a 3.5min long 4k canon clog3 clip, and I keep trying to use the noise reduction on my second node, after a CST. Ive turned on Node cache and it took about 20-30mins to render the NR. The blue line went across really slowly but it got there. Then I had smooth playback. I can adjust nodes further down the chain without any issues. I saved the project a few days ago and have just gone back to it. The best I can get is about 12fps playback at half resolution. Full resolution (1080p timeline) drops to 1-3fps. This is totally unusable. The thing I cant figure out is why. The node cache is on, and the cache manager is showing a big file, so it's still cached, only it's not. Render cache is switched to user, but nothing is getting rendered. The number on the Node is now red again, but it's not re rendering anything.
What am I missing? This isn't the first time ive had to waste yet more time letting this node re render (had to do it about 4 times on the first day, as it kept re rendering. Nothing has been touched in the first node, and no cuts or edits done to the single clip.