When multiple tracks are selected, audio quality degrades and CPU usage spikes

[kaiestro]

Steps to reproduce (on my Windows 10 64bit reaper):

Load up some tracks with cpu-chugging vsts like Serum in a fairly complex project (30+ tracks)
Start playback. The project should be able to play fine with no audio distortion at your chosen sampling rate.
Then select several heavy hitting tracks and for me, at this point the audio degradation would start and the play head would move more slowly, as if you dont have enough CPU to run the project at that sampling rate.
Note that I do have them set to automatic record arm when track selected, so maybe they are all trying to read their midi inputs at once causing an issue. Idk.

[airon]

That's a little unusual for midi recording.

You might want to post this in the General forum with a title that specifies the plugin you're using as well. More eyeballs might mean a quicker solution.