This is most likely due to the having a number of looping sounds attempting to play after loading in at once (even beyond audible range. In fact, this can exacerbate if they attempt to play immediately prior to closer ones playing) and/or how it reacts to the new Virtual Loop feature.
The following commands are available for tweaking whether the feature is enabled or disabled (recommended to leave on as its a big performance win when your level has lots of ambient looping actors), the distance between listener and source used to scale how often virtualization/realization swapping is checked, and the respective minimum and maximum update rates (which default to 0.1s and 3.0s).
Once you have tweaked these to your liking, you can either set them directly in code/script or set them and leave them from an .ini file.
Alternatively, once your player has spawned in and is ready, you can call something like the following to force the virtual loops to all update state immediately:
if (FAudioDevice* AudioDevice = GEngine->GetActiveAudioDevice())