What you were expecting to happen, and what actually happened?
I switched my PvP defence team to another one (in a different team slot). I expected it to stay on the newly selected one, but it keeps switching to previous week defence. I tried exiting PvP menu right after the change, fighting a Ranked PvP battle in-between, making the change through Edit teams menu - all for naught. I had a similar problem last week and somehow it finally stuck, but I really have no idea what was the trick exactly. Any suggestions? Not to mention it should be pretty easy to do...
What are the steps to make it happen again?
Pretty simplistic: change your defence team (to another team slot), exit PvP menu, enter it again. It's reset back to the old team slot
Do you have any screenshots or video you want to share with us so we can see the problem? Attach them to your post!
EDIT: OK, so I experimented a bit more. I used the Edit teams button again and changed the team name - this time the new defence seems to be permanently set. I'm pretty sure changing anything in the new team would do the trick, but I'm not really up to more testing right now.