Certain Gen 1 tradeback movesets from Gen 2 flagged as illegal?

[MeterGriffin]

So when editing certain Pokemon in gen 1 with gen 2 tradeback movesets allowed, it still flags some of them as illegal, but not all of them, shown in the images. Does anyone know what's causing this? Thanks

[theSLAYER]

@MeterGriffin I can only assume you're doing something wrong..

Using my legal Gengar, I changed the Catch Rate to match it's original value, and it became illegal.
Thus, I'm guessing that your Gengar has it's default catch rate (of either Gastly's 190 or Haunter's 90)

One thing you need to know, is that Catch Rate in Gen 1 is actually used as Held Item in Gen 2.
However, not every value corresponds to a possible item in Gen 2.

So for the example above, 90 actually doesn't correspond to an item, so if you indeed traded Gengar to Gen 2, it's Catch Rate gets forcibly overwritten by the game.
Gen 2 would force the held item to be Berry. Of course you can opt to remove the item from Gengar. In any case, it's Catch Rate would no longer be 90 when traded back.

Based on that, PKHeX can tell that you didn't perform a tradeback, hence it is right to flag your Gengar as illegal.

(It's the same if it was evolved from a Gastly; has 190 as Catch rate. 190 doesn't correspond to an item.
List of Gen 1 held items, list of Catch rates, and big list of indexes and item)

 

edit: if the issue isn't the catch rate, then upload the Pokémon.

[MeterGriffin]

Yeah you were right, it was the catch rate. Thanks for your help. 

[theSLAYER]

54 minutes ago, MeterGriffin said:

Yeah you were right, it was the catch rate. Thanks for your help. 

glad I've been able to help