This issue has occurred recently after an update but I don't know if that is the core of the problem, it hasn't happened before in this way.
Opening up any project and the preview screen and audio meter either are frozen or lagging/ the frames drop for both. (The audio plays all through fine but it seems to be an issue with the video output.
When I open a separate sequence and play footage there and go back into my main project sequence it is fixed. It does not work if I open media in the sequence with the occurred issue.
Error or problem
Freeze or hang
User interface or workspaces