Sheila's original video is ~2sec footage of fast shutter, supposedly at 150 fps according to the file metadata.

Attached is an edited video that shows the 50ms of FS action slowed down by a factor of 10. "SRC TC" is the time elapsed since the start of (Sheila's original) video multiplied by a factor of 10, i.e. 1 sec in SRC TC is actually 100ms. This timestamp is not to be trusted at the lowest digit of sub-second (ms level in reality) because there's some frame interpolation going on due to mismatch between the standard output frame rate of 24FPS VS the source frame rate (150 slowed down to 15 FPS). Anyway, the mirror goes down lower than the closed position right after the initial thrust of the HV fast shutter motion, and even a few bounces after that, before the shutter eventually settles to the permanently closed position.

Also attached is an annotated png file of four frames ("Open", "HV thrust", "Bounce to the bottom" and "Close").

In light of recent failure of the replacement FS at LLO where the mirror broke off due to the hard stops that were set too low, and a comment by Rich (LLO alog 73584) I watched the video of the LHO unit again (see my entry above).

Though LHO video was shot from the side where we cannot see the position of the hard stop, the bobbin might be hitting the stops right after the launch even though the height of the stops looks good to my eyes. See TC~00:00:05:06. And the bobbing oscillates several times though it never hits the stops again.

Does this mean that the magnetic braking is too weak?