Hi Stephanie,
I think the same issue came up a while back on the forum:
The main takeaway, if I’m not mistaken, was that coverslip coating prior to plating was key, and that a fresh batch of Laminin solved the issue at hand.
My own personal anecdata: I follow a similar pre-coating protocol outlined by Alex in that post and I usually don’t have any issues with detachment. I also cut a few corners, ie washing twice instead of three times and using straight PBS instead of PBS-tween for my primary and secondary dilutions. No experience with CaCl or MgGl to add to the conversation unfortunately. Good luck!