I have a guardian farm that I afk at for a while. When I leave, I'll find up to 10 guardians floating in the air below the farm. As soon as they notice me, they stop floating and fall. They usually appear after about 10-30 minutes of AFK-ing. If you're unable to replicate this bug, I'd be happy to send you my world.

More details: If you search "Minecraft bedrock guardian farm" on YouTube, the one I use is the one shown in the video posted by "JC Plays." (or maybe it's "Playz;" I can't remember.)

If I shoot the Guardians, they take knockback but continue to float in the sky as long as they don't notice me. They sometimes start to go up and down as if hanging from a lead after being shot.