Updating Custom Traits Using Mod Constructor

2020 was Snowy Escape, the first major patch since...Cats & Dogs maybe? that wrecked traits, then there was one after recently that I can't currently remember (DhD?). If you updated MC4 after those patches when Zerbu announced it and re-exported, that should have fixed anything related to patches. If it's still throwing errors, the problem is likely related to how it was made then.
But it's been a while, if you haven't tried it recently I recommend trying again: zerbu.tumblr.com/post/181782526135/the-sims-4-mod-constructor-v4
Otherwise you should re-make your custom trait in MC5: github.com/Zerbu/Mod-Constructor-5

As for the custom traits from other creators, unless you have the MC project files you cannot update them with MC. You will have to open them in Sims4Studio and fix them that way. Or, the alternative is to re-make them in MC5 or find traits from other creators who do something similar.

Running a "Patch Day" scan with BE would list any tuning related issues for the traits. Then you just need to find the listed section in the trait (or other involved files) and fix it based on what it's saying, combined with the TDESC (official documentation from EA): tdesc.lot51.cc/Traits/Descriptions/Trait.tdesc
Although taking a quick look at the BE Patch Scanner, TEN from Scumbumbo might work better depending on the errors you're experiencing: scumbumbomods.com/tuning-error-notifier/
Editing Guide: chii.modthesims.info/getfile.php?file=1828288

If you still need help, come back and link the traits that are broken and the error report.