Hmm .. Quite old version and not even the latest patchlevel in the Mavericks release tree.
When looking at summaries of Mac OS X then 10.11 shall have got enhancements in terms of stability and speed.
Can you make something like a disk image and look whether this behavior changes with 10.10 and 10.11 or even newer versions ?
Maybe you can stay on 10.11 and go back to 10.9 if things are not working for you.
It says "never touch a running system" but staying on an old system for too long can also have disadvantages.
10.9.3 is also not the latest patchlevel of the 10.9 tree.
But do this only if you really can be sure to go back to current status.
On a PC I would ensure this with a good Disk Imaging program like Macrium Reflect.
I would ask in this forum and in the forum of your DAW software which more up to date
version of Mac OS X runs best without major issues. And if possible I would always use the latest patchlevel.
BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub13