A friend of mine uses Cakewalk on a new Windows 10 PC (actually not 100% new, some sort of refurbished PC).
Cakewalk seems to work fine, except for one thing:
You play an audio musical track (or video clip with audio) in any media player (Youtube, Groove, Audacity...).
While the audio is playing in the background, you open Cakewalk. (Background audio remains fine.)
While the audio is still playing, you open (not play) a Cakewalk Project.
At this point, you may hear some audio glitch (or not), and then suddenly, the audio being played in the background by the other software slows down a little bit and the pitch goes down by one or two tones.
If you close Cakewalk, the audio in the background remains low. However, if you pause and resume playing, then the audio gets back to normal speed & pitch.
The most amazing thing: if it's a video, although the audio slows down, the video remains synchronized.
He uses an old external sound card: Tascam US-144 MKII. It used to work fine with its former PC (Windows 7). The soundcard is supposed to be Windows 10-compatible. However, I could not find on the Tascam website a driver explicitly meant for Windows 10, so I'm not sure. However, if there was a compatibility issue between the soundcard & Windows 10, it's still strange that it mostly works (for Cakewalk, and for other software, just not at the same time). I might test my own soundcard on his PC to see what happens.
When the main Windows sound device is set to the PC default sound device, opening a Cakewalk project doesn't affect other audio clips played in the background (while Cakewalk still uses the external sound card as sound device).
I have tested various settings in Cakewalk, including all drivers available, but only ASIO seemed to work.
Let me know if you can help, and if I need to provide other technical information.