I did notice that red light and figured it was recording while it was flashing. I will definitely try testing it this way. Thank you! And I'll try to see if I can look at the files in a different viewer (my advisor has Kaleidoscope so we'll try that). Thanks for all the help!!

Sadly, I don't. The issue is that I can't even open a lot of my files to see if they contain bat calls because they are too "large" for the WAV file viewer I'm using (Sonobat). Do you know of any other WAV file viewers that would be able to view 26,000+ kB files? Thank you for the recommendations though! I will definitely test out both increasing the amplitude threshold and increasing the filter cut-off frequency (in separate trials). The good news is that we are getting bat calls, but the large number of these unviewable files is a bit concerning!