OPie Taylor said it was when he fretted...i.e. before plucking....
Either A or B or both...
A. Action way too low.
B. You are working waaaaaaaaaaaaay too hard fretting a note. Play the frets, not the board. You will touch the board but that is NOT the focal point, the fret is.
Have it set up by a tech (good idea anyway) and if possible, play it in front of tech and ask them what they think you are doing incorrectly...
My late big bro played bass for close to fifty years. He preached to me from when I was just a little crumb snatcher, conservation of energy. Use just enough to play the note/phrase and no more...unless dynamics call for more at a spot then after, back off. Work on touch while playing notes....slowly.
Tips I got from him: Never 'slap' a fret hand finger down on a note to fret it (unless called for) as it WILL snap, crackle, pop...and most folks have four fingers on their fretting hand. Use all four.. Conservation of energy... Never slide up and down with the index finger. Force yourself to use all fingers available...
Get a veteran bass player to teach you a couple of slow 'lounge walks' with the backward downs... Those are some of the best exercises on the planet one can play to limber up fingers, improve touch and accuracy, crossing strings up and down, and stretching fingers...and to listen too....
And get a metronome. Most folks hate a metronome because a metronome will light your ass up every time you daydream... Some just toss the metronome in a box because of their own timing issues, not the metronome... One of the funniest things I've heard "I can't play with a metronome at all but I have perfect time...ask my drummer." Says a lot for both he and the drummer...
Enough of my blathering.....
Good luck with fixin what needs fixin.... and learning bass...