Spin Off PMD Rescue Team DX: cant friend shedinja and shinies in dungeons, how to do ?

[Kadaj]

i havent had many problems getting random pokemon to join the team for me (even kecleon), but theres two things that seem down near impossible to friend in this game: shinies and shedinja. ive found many of both here, shedinja even more so (these can be seen in over half the post game optional dungeons where i was questing offline) but no matter how many of these i beat they never seem to join me. the only shinies i have are a shiny noctowl (idk how i did this either, just lucky probably) and a shiny celebi (you can find her in a mystery house after beating purity forest, idk if there are location specifics though). but not a single shedinja whatsoever.

i think i know how to get shedinja, but the shinies seem to have a near 0% friend rate. i also cant seem to find shedinja as an RNG fainted pokemon either for some reason, i know for sure how to get him in the main games (its very easy there lol) but i dont know why him and shinies seem to have worse friendship rates than kecleon in this game, is there something very specific i need to do? i see lots of other people playing this remake who have way more shinies than me and im not sure why everything but these (and shedinjas) will join me like a kids joke, ive rerun the corresponding dungeons numerous times beating random quests but they seem impossible... help?