It doesnt have to be full happiness for Oak to accept it. That you traded it is also not the issue as I traded multiple starters for the quest and never had a problem doing so.
Dont know what else could be wrong here though.
Already has been suggested a couple times. I think the repel price should stay as its a good money sink but Max repel should be adjusted so it has the same cost per step as super repel.
Little off-topic but I was wanted to let you know that Suzuka Cave from your suggestion on that thread is just an exclusive area from the easter map 2020.
Thats because you talked to the Hunt Event NPC. This Scyther is the current record holder. The problem you experienced is because the preview of that pokemon will just show up minutes later after actually talking to the NPC.