Alright, as it turns out...I'm apparently an idiot.
Turns out that by some coincidence, the two sound files I was trying to use are somehow "corrupted"...didn't download properly.. of something. Either way, I have no idea.
I once again made sure that everything in the user folder was clear, then tried a different, random music file altogether that I downloaded from free-stock-music and it seems to be working fine. The previous files were from Zapsplat, which I have used before...so like I said...I have no idea what went wrong.
I tried to import the previous music file, which I originally tried, and yes...in wav format, which I converted with Audacity...and it crashes again. Tried the 2nd of my original attempted audio file...also crashes.
I also tried importing another music file as an mp3 and verified that it converts it to wav automatically, with no issues.
So, as it turns out...I'm just a big dummy.
Sorry for wasting everyone's time.