Volatility is out of control in MBS's. Just after 9AM, the 5.5% coupon almost touched 101-00!!!!!
It is now down to 100-06/07
So, if your lender already released rates, and especially if your rate sheet hit before 9:30 AM but after 9AM, you probably won't lose any money today if you lock. If, like most lenders, you don't have rates yet, keep floating and wait for more info. Here's a graph that shows the current volatility.