I'm running Studio One 4 Professional on a Surface Pro 4 with Windows 10.
When I start a new session of Studio One, all audio will play back with a constant crackle. It does not matter whether the playback is MIDI or recorded audio.
I can immediately fix the crackle if I change the current Audio Processing Settings to anything other than what Studio One loaded at start.
For example, if Studio One loads with Dropout Protection set to "minimum", the crackling will stop if I change this to "maximum". However, if I load a new session of Studio One with Dropout Protection at "maximum", crackling recurs and is now fixed if I change Dropout Protection to "minimum".
Similarly, if Studio One loads with Process Precision at "Single (32 bit)", crackling will fix if I change this to "Double (64 bit)". While, if Studio One loads with Process Precision at "Double (64 bit)", crackling will fix if I change this to "Single (32 bit)".
The settings are independent. I can change either Dropout Protection or Process Precision from its current setting and the issue will immediately resolve. I do not need to change both and it doesn't matter what the settings are when Studio One loads.
Within a session, the crackle will return if I return to an original setting. For example, if Studio One loads with a crackle at "minimum" Dropout Protection and I fix this by changing to "maximum", the crackle will return if I switch back to "minimum" before closing Studio One. It's only if I close and restart Studio One with "maximum" Dropout Protection that audio will then play back correctly when I change the setting to "minimum".
So, Studio One will produce clean audio on any setting for Dropout Protection and Process Precision but only if the current setting for either is different to whatever was loaded at initialization.