I have audio that is redlining, but the audio thumbnails are so small as to be useless (little more than a thick black line).

To be clear: there is an audio thumbnail for each clip, it's just really, really, really small even when the audio is really, really, really high.

Absolutely no idea why this is occurring (it didn't used to), so any ideas on what may be behind the glitch.

Since syncing by audio cues isn't working either, this makes syncing multi-track videos really difficult.

Currently using:
Kdenlive 16.12.0
KDE frameworks 5.18.0
Qt 5.5.1
MLT 6.3.0
on Ubuntu 16.04

The solution is to switch to the non-ffmpeg method of rendering them in the settings/timeline

Video tutorial: https://www.youtube.com/watch?v=UKslOkep9g0