Terry here again.
sorry to hear replacing the flex lines did not solve your problem.
we are going to have to narrow down where the fluid is locking up.
so start at the top,the master cylinder, and open the lines up to see where the pressure build up is.
for example: the front brakes are locked, you open the line at the master cylinder and the pressure releases. than it must be the master thats not releasing the pressure.
I'm sure you'll find it using this method and theres no charge for this answer