If you scroll slowly with the scroll wheel through your hotbar on macOS, the slots are only changed every 5 - 10 scrolls and sometimes not at all. You have to move the mouse wheel very fast to scroll through your hotbar and some slots are skipped because of this, which makes playing very frustrating. This bug exists since the release version of 1.13.
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Can confirm: It is very noticeable if you scroll slowly, as when you try to change to the hotbar neighbor not to trigger a two or more slots jump. I have to either use number shortcuts or scroll the entire hotbar to get where I want to with precision.
Does MC-154903 describe your issue?
This is a duplicate of MC-154903, you have to enable the "Discrete Scrolling" option in Options → Controls → Mouse settings
Does MC-121772 describe your issue? Reported around 1.13.