What was happening is that the "procedural" real-time buffer was not submitting the 3rd PCM buffer (like the old streaming audio bug I fixed a few months ago). The problem was that it was thinking it was going to be asynchronously decoded, but it wasn't. There's other issues in that sound cue node they wrote, but the issue reported here should now be fixed.
When playing a sound with the bProcedural = true option enabled. The associated sound will then drop samples when played. The licensee who originally reported the issue actually has provided a fix in code to work around this issue.
I have attached an image of the licensee's comments which includes the block of code for the fix.
He also provided a video example of this issue not occurring in their 4.8.3 project, and an example of this occurring in an isolated test case in 4.9.2.
1. Download and Open the attached ProceduralSoundBug project.
2. Open the custom sound cue named SC_M249_1P_Looping.
3. With the 'Squad Full Auto Looping' node selected in the Sound Cue editor, tick the 'Disable Generate PCMData Count'
4. Press PIE
5. Fire Weapon and listen for the sound cutting in and out.
6. Now untick the option and press PIE again.
Outcome: Sound Plays as expected
Expected: The 'Disable Generate PCMData Count' option will not have an effect of the sounds playback.
Head over to the existing Questions & Answers thread and let us know what's up.