CONF,
I admit to being baffled by the SEL'D VS trace.
The 'zipper' before the AP disconnect looks like an FDR or postprocessing graph software artefact (as suggested), but why does it jump to +5000ft/min shortly after the disconnect, and then drop abruptly back to approx. zero?
I seem to remember somebody saying earlier that it was not the 'raw' MCP setting, but an 'intermediate' parameter.
Isn't it a red herring, if the AP/FD was in ALT CRZ mode?
I'm not 'au fait' enough with the Airbus FCS.