first, let me get into (GIT instructor) sid jacobs' guitar-technique/billiard analogy:
GOOD billiard players always "seem" to end up with a great next shot after sinking in their balls. while this might appear as simply good luck to losers like me, it is indeed a consequence of them already thinking ahead to the next shot while they play their current one.
this will make or break a good player (just think of chess!). same as in right hand technique, especially for us bass players.
let's assume, we're only concerned with the note we play at any given instance - our playing (in slow motion) would look something like this:
now let's assume, we follow each note with an ultra-fast preparation of the next note (meaning whichever finger is up next actually gets on the string and is ready to pluck it). then our (slow) playing might look like this:
based on that principle, I practice the following exercises: 1st, I play 4 notes on every string, from low to high and back (video is restricted to 4 strings, but apply it to as many as you have):
note that when descending across the strings, I "rake", meaning I "reuse" the last finger of any string on the next lower one. now I play only 3 notes per string:
now only 2 notes per string:
and finally, the "king of string crossing exercises": 1 note per string!
let me assure you: those exercises DO work IF you do them
very often and very slow!
think of the whole process as "programming" your brain - no piece software is
ever written as fast as it is executed, right?
you'll notice much more reliability and precision in your playing soon, as long as you follow the finger plucking order religiously in your practice.
GOOD LUCK and BE PATIENT!!!