I put Oasis warm nylons on my Pono MTD, and every now and then there is a buzz on the e string. I checked the saddle and there does not appear to be a notch for the string like on strings 3 and 4. If I take a file and notch it a bid would that resolve it?
I don't see why that would fix it. So I'll go with "no". Although some instruments (not usually ukes) use notches in saddles on purpose, normally they are there because of the tension of the strings down on them causing wear. They can even cause issues if they get too deep, etc.
If that string is lower tension than the strings you had on it before, that might explain the buzz as the string would have more movement to it. Buzzes are pretty hard to zero in on sometimes though.
If this is when the string is played open only, it could also mean the nut slot is too wide if you've gone to a string more narrow than what it was setup for. You may also try to clean that slot, make sure there's no debris in it, etc. Lightly run something through it, even a folded piece of paper.
Correct break angle there is important too.
If it happens on random fretted notes, that's a whole other thing...It could be my first guess up there. It could be revealing some frets that weren't quite level that wouldn't show up with a higher tension string.
Before doing anything, give it a few days to settle in with the new strings.
Of course there's a possibility that there is something wrong with the particular string too.
Those are all my guesses I think. I hope you get it figured out.