Trouble shooting glitchy playback nothing has changed

All of a sudden Resolve is starting to play back the footage in my project very slow, skipping frames and delay.
I have not changed any settings. I am aware it could be a number of things, but where do I start to troubleshoot the issue.
I'm working with 4k BRAW footage, which normally plays back very smoothly on my system even when there are grades and effects on top. I normally only start to get playback issues when I denoise or sharpe, and this problem is happening with ungraded clips.
I have not changed any settings. I am aware it could be a number of things, but where do I start to troubleshoot the issue.
I'm working with 4k BRAW footage, which normally plays back very smoothly on my system even when there are grades and effects on top. I normally only start to get playback issues when I denoise or sharpe, and this problem is happening with ungraded clips.