I know this is an old thread, but it was happening to me with Studio One 4.5 and I figured out a few things. Save was taking 30-40 seconds on the most basic 2 or 3 track songs. If I would save while playback, meters would freeze and I would be locked out of all interactions with the software. I started disabling everything I could think .... virus, firewall , etc. but when I disabled the wi-fi adapter in the device manager WIN10. it started saving normally, like in a half second! So I closed S1 and that took 2 sec instead of 30. Then I restarted and S1 4.5 stalled on "starting VST 2.4 plugin support". The message was "waiting for plug in scan process" . After 5 minutes I hit cancel and S1 started but was missing Console 1 , Focusrite, and Melodyne plug ins. Only Presonus plug-ins loaded. So..... my work around is this: I start S1 with wifi enabled and then disable wi-fi adapter in the device manager to actually record , save mix save etc.
My guess is that the problem is with Softube, or Waves plug ins that I only use in Nuendo. I know Waves is notorious for spying and licence checking. Nuendo stalls for 3 minutes or more while checking every Waves plug in licence.
Just to see if there was snooping going on, I pulled the plug on my incoming DSL and started S1 before Windows realized there was no internet. It started just fine... So much for the snooping theory.
One more thing..... After being up and running with my work around, I went to the plug in manager and pressed "update plug ins" and without wi-fi enabled it stalled with the "waiting for plug in scan process" message until I hit cancel.
I did a lot of changes at once. I updated to latest win10, Studio One 4.5, turned off automatic updates with WUP . I don't have my ilok plugged in because I'm not using the Waves plug-ins on this computer, and my Softube Console 1 is also on my other computer but that didn't matter before.