Hi @Jake-B, if the automation 'mute' process may be switching it. It could have been enabled inadvertently. I did this once and took me a while to find the cause.
The automation track volume envelope tool cause it as well and could be visually unnoticed if the volume envelope line is hidden (keyboard shortcut: 'V' key).

Good idea of checking the volume envelope, but it's unchanging throughout the project. Not sure precisely what you mean by the 'mute' process, I checked that there wasn't an audio mute envelope on the track hidden away somewhere and that's not the case either. I had a thought that maybe something different would happen if multiple audio tracks were playing at the same time (at least something different enough to offer more information) but that didn't change anything unfortunately. The tracks that had audio issues still do but now another track is playing at the same time, that's all.

To follow up on my original post, I can hear the audio in question just fine in the raw footage, the waveform in the audio track(s) looks accurate, but when I preview or render the project it just goes silent at certain points. These points are seemingly at random, but they will occasionally change when I edit a clip, causing the correct audio to come back but these changes can also cause another piece of audio to leave. It doesn't seem to correspond to a particular timestamp as I've tried moving the tracks around or lengthening/shortening them to no avail.

@Jake-B Do you have any 3rd party audio effects in the project?

@Jake-B Do you have any 3rd party audio effects in the project?

Nope, I just started editing it more or less so it's just the base video trimmed up and a few clips moved around.

Could you share MediaInfo for the source video? Sounds like VEGAS is having trouble decoding it.

Unique ID                                : 140548235119324876610995553255329851463 (0x69BC9AFFBC321BAEE1A220D43EB36847)
Format                                   : Matroska
Format version                           : Version 4
File size                                : 11.0 GiB
Duration                                 : 3 h 0 min
Overall bit rate                         : 8 773 kb/s
Frame rate                               : 60.000 FPS
Writing application                      : Lavf61.1.100
Writing library                          : Lavf61.1.100
ErrorDetectionType                       : Per level 1

Deleted the complete name because I know it's not relevant but other than that I changed nothing about the output. There was another part above this text block that wouldn't copy in a clean way so here's a snip of it in case it helps:

The text view of MediaInfo is more useful for this but working with what's here it looks like MKV.

I'd avoid MKV containers as it really varies whether they will work in VEGAS. Can you remux the AVC/AAC contents to MP4 using either the software you created this with (OBS?) or a tool like ShutterEncoder? https://www.shutterencoder.com/

It was in fact a .mkv file so I remuxed it with OBS to get the mp4 file and it SEEMS to have worked. I'm going to have to redo the trimming work I had already done when I realized there was an issue and through the course of that I'll find out for sure if it did or not. I feel confident that this is the cause of the problem but I want to be sure before I mark it as the solution. Thanks a ton for the advice!