Lakka Pi4 PPSSPP Slowdown/Stutter/Lag

Hi I have a new Pi4 (4GB, overclocked CPU 2,000 GPU 600, with both passive and active cooling). It is running the latest Lakka build 2.3.1 and I’m having a couple of teething problems with the PPSSPP core. Hopefully someone here can help. Several games stutter. This doesn’t seem to be lag in the usual sense, there are long pauses up to a couple of seconds long that occur while playing the game. Tomb Raider Anniversary and Medieval both experience this quite badly.