There's a whole list of things that can be causing drop targets to drop when resetting. Among them: Weak Spring; Arm that pushes up has divots worn into it; gummed up reset actuator' Lip edge on targets are not sharp.

There's several threads out there about drop targets "bricking". Those threads may also give you some insight. Based on what I see from the video, I would go with weak springs and/or worn drop targets.

The tracks the metal drop target arms run in could be worn too.

Not part of the problem, but Mata Haris originally came with "tombstone" drop targets.