Originally Posted by DozyW
My theory is that the values on the trace are also calculated in real-time and those large bumps just before disconnect are a result of what the V/S *will be* if the current trajectory is continued, the pitch is retained and/or corrections are not made.
Based on the close correlation of normal acceleration, V/S and altitude (each being either the time-derivative or the integral function of one of the others), I don't think the traces support that theory.
According to FCOM 1.31.40 p.15 description of indications on PFD:
The displayed vertical speed information is normally based on both inertial and barometric data.