the zipper shape of the selected V/S trace BEFORE AP DISC
IMO you can skip this concern from the list.
The 'zipper' means it is - not active - (AP was in ALT HLD mode not in V/S mode)
You can notice identical 'zippers' to est. slide slip trace - after law change - de estimated slide slip is not calculated in ALT LAW.
The selected MACH trace - Page 109/110 BEA IR#3 EN - shows the 'zipper' too.
This trace for whole flight @ page 110 shows dark area but actually these are 'zippers'.
Also 'zippers' on the other parameters related to AS when these were NCD.
Why - the not active state - is reflected as zipper I don't know, maybe due to a reset signal to distinct from a steady 0 value?