What you suggested worked, but when I tried it with a second .mp3, it caused the app to crash again, and the first .mp3 would crash now too. So I deleted both files and started again and now the first mp3 crashes the app.
here’s the link for the first file http://zapsplat.net/zapsplat-sounds/download.php?fileName=pm_rd_rain_23_city_modarate_drippy_362.mp3&expiry=1581591517
because I’m using an iPad the file browser doesn’t let me show a file tree, but I have put the files in epicGM>sounds>AMB