May I suggest a reboot of your PC, reboot of sonar.
Something could be corrupt and being held in RAM.
Restart the computer to erase the RAM memory. RAM is a volatile memory means as soon as one turns off the system the RAM gets free from the applications currently running on the system and again turning on the system resets the RAM again.
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Also make sure your windows updates have all recently been run (are up to date).
It could also be another application you are running along with sonar.
If you still have the problem-
Do a few tests:
Try a new project
Try this over audio
Try this over midi