As I know, DIKO uses CCE for encoding and it seems that this is not an Packshot issue BUT a mencoder Issue when authoring mencoder generated files using DVDlabpro beta versions!
All other DVD authoring apps do not have any Probs with Mencoder m2vs, like MaestroDVD, TmpgEnc DVD author, ... etc.
I dropped DVDlab(pro) cause ...
a) buggy!
b) to slow when authoring/muxing
c) Much nice stuff for play, means many menue creating options. BUT they FIRST should getting main engines work properly before developing useful extra "toys"

d) A TOOOOTALLY complicated way if generating a DVD using multiple VTS Tracks! Even in Pro Version (do look at their Tips/Tricks page - that workout to get 2 VTS Tracks working is a JOKE!)
and
e) too sensible according to incoming streams as you see in your case above. In the Mediachance forum they say "Do add Closed GOP feature and it will be ok" ....

For what the hell I do need closed GOP feature if NOT authoring more featured DVDs ??
You see I made my count with mediachance.
Do look at MaestroDVD and you see where the at least full working roots of DVDlab are from.

Inc.
PS: I see you go into Packshot/mencoder using an full field/blended/dynPhaseshifted Simpsons Stream!
In small words

Interlaced Source ... and Packshot in its actual state doesnt support interlaced encoding.
BUT as I also some time ago did a " mistake" by encoding progressive a similair case (Independence day - also bad NTSC/PAL converted and therefore full interlaced) ... I did a try and just patched the encoding to a interlaced stream in its flag settings using Restream .... and it played back with NO Problems!
Totally crazy but it worked even when that mistake by choosing the wrong encode mode was done