The only major pitfall to watch out for now is passing down an impossible ball, such as Safari Ball or Sport Ball prior to Home opening up for transfers (and after it opens up, those balls will still be impossible for newly introduced evolution lines like Baxcalibur). Most notably, the Paldea starter lines have not been made available to *catch* in any raids or otherwise, and unless and until they are, those species can only ever have the standard Poke Ball because that's what the gift starter at the beginning of the game comes in.
In the past, it was also possible to pass down hidden abilities on species like Litten and Passimian before those abilities were legal (but now, in the era of the Ability Patch, this is a non-issue as everything in the game that has a distinct HA now also has guaranteed access to it), or impossible combinations of egg moves (which again were phased out as a factor after mothers became eligible to pass down egg moves, and later the use of picnic transfer for moves made it even more convenient).
