it's not a bug, you can ONLY get reward from TIs 20 times a week (+ an extra 5 times if you do it with someone with lv5 or above friendship). It has ALWAYS been that way. So 25 attempts at most a week, and you can do 10 one of the day if you team with friend(s) of high friendship level. If you do max of what you can everyday, by Thursday you'd have finished all your rewarding attempts. You can still do TIs after that (for other activity requirements like great tree, weekends mission, etc.), you just won't get the card spin rewards for them.

As has been explained above, there is a maximum amount of times per week in which you can receive rewards from completing Team Instance per week. You can check how many reward attempts you have by checking the Rewarding Attempts which is located right below the Conditions in the Daily Practice Interface.