Voice memos not playing after renaming- need more detailed advice

I am a director who needs to submit student auditions to an organization for judging. Their auditions are recorded using voice memos on my phone. I had several auditions suddenly become unplayable after renaming them to the naming convention specified by the organization. This has happened twice now. (I re-recorded those auditions and they became unplayable yet again after renaming them) I have already force restarted the app, I have force restarted my phone, I've updated my iOS, I've tried to see if I could access the recordings though another app, nothing seems to be working. I'm bumping up against a deadline and need to know if there's any way to recover these files, and how to prevent this from happening again. For context, the naming convention used for these recordings is something like the following (specific numbers are changed for audition confidentiality sake): "elem.024.6"

Is there something in the naming convention that could have glitched out my recordings? They just won't play. The play button is unresponsive; when I go to "edit" the audio, it shows no waveform display. When I try to have it transcribe audio, it will say it cannot, but after exiting that function, I can see the waveform display in the editing window but it still won't play. I tried renaming a test recording a few different things and it was still playable after, but when I used the same naming convention with a different specific audition number (single digit at the end) it suddenly became unplayable.

How can I fix this? Or at the bare minimum, prevent it from happening again?

Device details:

iPhone 16

iOS 18.7.1 (updated literally 5 minutes ago from previous version)

Thank you for any and all help you can provide.