The Pro-Channel version I have is 1.3.8. There is no save issue on my machine.
I never install the saturation knob with my other Softube plugs since it was included with Sonar at some point in time.
In order to see if I could duplicate your issue, I installed the saturation knob by the Softube Plug-Ins Control app.
After the usual VST scan, the Sonar version was still 1.3.8 in the PC and Sonar crashed when I tried to play the small project.
I removed the saturation knob from the "C:\Program Files\Cakewalk\Shared Utilities\Internal" folder and rescanned.
The PC version was then 2.3.41 and Sonar played as is typical.
Tweaked the saturation knob settings and closed the file. I was prompted to save my changes. Reopened file. Settings was 0 on the saturation knob.
I can confirm that the action of hitting save moves the setting to 0 on the v2.3.41 of the PC instance.
I then replaced the 1.3.8 version in the internal folder and removed the VST2 saturation knob .dll. The VST3 and the older PC version coexist without issue and the older version keeps its setting as is usual.
I inserted the VST3 version of the saturation knob in the FX bin and in an FX chain in the PC both retain their setting on save and reopen.
Good luck.
Greg O