Are your flex hoses new too?
If not, one or more of them could be the cause of your locking if they are collapsed internally, and not releasing pressure.
If the flex hoses are new, you might have a frozen caliper on the front (do you have pull to one side?) which means the other caliper gets 2x the pressure, or the rear (inspect for uneven pad wear, etc).
It may just be me, but I fail to see how changing fluid will prevent locking up the brakes. Under normal everyday city streets driving*, the fluid is just distributing pressure to the four corners and one or the other won't make a huge difference. If a brake is locking up, more than its fair share of pressure is going to it or it is accumulating pressure with each stop. Changing fluid, unless you are going to a "more compressible" one, doesn't seem like the cure, especially with new components in the system.
*Then again, you might drive your 114 like it was a spirited BMW or something, and really work the pedals hard...