It are
interlaced frames that are missing (dup-replaced) in the source file. Therefore in the gaps there are 2 fields missing, hence you need to fill in 2 frames after bobbing.
Code:
ab cd ef gh ij kl mn op # (1) interlaced original
ab ab ef ef ij ij mn mn # (2) oddframes dropped, evenframes doubled
A B x x E F x x I J x x M N x x # (3) this is needed, but can't be constructed directly
A . . B x x E . . F x x I . . J x x M . . N x x # construct this (2 newframes for each),
0 1 2 3 4 5 0 1 2 3 4 5 0 1 2 3 4 5 0 1 2 3 4 5 # then select
With (2) being the source you're starting with.
Code:
# NTSC 30fps source
selectodd # to 15fps
bob # back to 30fps
assumefps(30)
InterFrame(Preset="Placebo",Tuning="Film",NewNum=90,NewDen=1,...) # tripling to 90fps
SelectEvery(6,0,3,4,5)
AssumeFPS(60000,1001) # now have reconstucted 60p.
No guarantee this works directly (cannot try now with your sample), but you see the principle.