not totally sure how helpful this will be, but just in case: I ran into a sample rate issue (which caused the kinds of issues you’re describing) with the 5moons recently & managed to sort it out this way: Introducing 5 Moons! - #30 by risibledog
EDIT: I guess if you want them to be 44.1k, you might need the command to look more like this tho:
ffmpeg -i input.wav -af "aformat=sample_fmts=s16:sample_rates=44100" output.wav
the only difference is that this one has the sample rate at 44100, whereas the other one has it at 48000, which is what 5moons wants.