It kind of looks to me like nothing more than a brown-out. The stuttering and flickery RSL are the normal symptoms of brownout, and a difference in gearbox sound (because you aren't giving the motors your normal 11-13 volts) is expected. If your battery read as 39% (3.9V?) then you were probably well below brownout levels.
The fact that no one else mentioned this has me worried that I missed something obvious though
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2016
| Innovation In Controls, Industrial Design, Quality Award, NC District - 4th Seed