To add some information, here are a couple of screen grabs of the RELPOSNED message at different times (antennas were stationary)
And no, this example with a 82m baseline was not the one I used a tape measure on :-)
One float solution, with 1cm accuracy noted:
A while later, another Float solution, still with 1cm accuracy claimed but more than a meter different relative position:
A while later, a FIXED solution, also 1cm accuracy noted:
They cant all be right...