UTAU-Synth isn't generating .frq files

[cactuscat15]

I'm completely new here so sorry if I've posted this in the wrong place. I've been trying to make a VCV voicebank on UTAU-Synth but some of the .frq files aren't being generated. I'm using 16-bit .wav audio files and have clicked 'update .frq' on all of them, but nothing seems to have worked. I've been using UTAU-Synth for a few years now and have never had a problem like this before. The odd thing is that the first few sounds of a recording have one, which sounds fine, but the last few sounds of the same recording don't, and whenever I try and play those sounds they sound really weirdly pitched. Any help would be really appreciated!