This may sound odd, but in your opinion do you think it is possible for someone/something who is astrally projecting to enter your dreams?
Maybe you can also project unconciously during your dreams, I think this may have happened to me, caused me to become semi lucid, it was really vivid, like the person was visiting me and had the control (I know them, and i was non/partially lucid, so not fully in concious control)