To answer many of those questions :
My two fingers have different "tones", so to speak.
When playing fast, I begin with a nice tone and good rhythm. As I keep playing fast, my plucking fingers start to wear out a bit, and my tone goes down as well as my speed.
The overall problem happens in some strings/places... This is because of my action on my bass, I got the bass with a bent neck, so I had to get it adjusted and straightened.
Usually, the G and E string are where I don't usually play consistently in volume. The E string, up above around 10th fret and G just about every fret and every time. But there is also a problem with the string, it's tighter than the other strings, by a lot, and the tuning peg itself is strange, I can't really explain it. It's as if there's some grime or rust just on that peg, and when you turn it, it doesn't feel the same... It's not as "silky", I guess.... I don't know if that's a problem or not, but I've been living with it for a year.
Hope this helps!
*this inconsistency is all at random, but only is some areas. Could it be my fretting hand that's dragging?