how to remove repeated frames from clip (doubles & sometimes sixtuples)?

[Jim_Pansen]

I've got some clips from a friend, very very old stuff.
Sadly, a number of frames are randomly doubled, sometimes sixtupled (!), a pattern can't be recognized.
So how can I remove all of the redundant frames inside the file (audio sync is not important)?

I have tried to test fdecimate, mdecimate & tdecimate.
Best result was with fdecimate, but it has repeated sometimes two following frames in the moment where doupes has been removed.

Any suggestion what function can help me better?

Thanks in advance

Jim