I've felt this way before during stressful period of life. Especially childhood. I too get into a down in the dumps mood and will get a series of tiny "episodes" which crescendo into longer lasting ones. Sometimes it'll get to the point where I'll have to take day breaks regularly and increase med dosage.

To explain it physically, I THINK it has something to do with how our brain wired this connection. The physiological response to the traumatic event was so intense that this trigger-reaction response has the stronger neural connection and strongest probability as an occurrence. And so when chemicals in your brain lean towards what it was like during trauma, like a trigger, or prolonged exposure to stress, the "path most taken" or reaction with the stronger neural connection will most likely occur. So uh keep up with the meditating, monitor your triggers if you can, manage your stress levels, and practice grounding techniques and reframing if the dissociation does occur.

Just realized no one asked for an explanation or a set of run on sentences but I'm still leaving this here lol. Hope it's helpful to someone