macOS: constant crackling/popping sounds in FMV's

[tycooko]

Hello,
I have a 2020 27'' iMac (3,8 GHz 8-Core Intel Core i7, AMD Radeon Pro 5700 XT 16 GB, 128 GB 2667 MHz DDR4) with Big Sur 11.2.
I've used both the official build for macOS that's on the PPSSPP's website (v1.6.3) and a build that a generous user here has compiled and provided for all of us, based on version 1.10.3.
Both work just fine, but during FMV's in several games I've tried (Final Fantasy IV, Crisis Core, Genso Suikoden I & II, etc.) there's a distinct and quite annoying crackling/popping sound, once every 3-4 seconds. This is only during pre-registered 2D cutscenes.
I've tried everything (select and deselect audio sync, frameskip, select all speed-up options, native resolution). Nothing seems to work.
What more can I do?