Description:

I was playing on a realm (may not work on normal worlds), alone, and I was doing raids a few hundred blocks away from my own village, once I had came back to my base, I drank some milk to get rid of any potion effects (I have had this bug in the past, but I thought it was the bad omen icon being invisible), as I entered my village, a raid began to start, I had no bad omen effect.

Summary:

Raids are starting without the bad omen effect.

How to replicate:

I'm not 100% sure on how to replicate it, but i'd assume that you'd have to: do a raid elsewhere, go to another village and then see if a raid starts.