If you deposit anything in your sP vault before collecting your interest, it will later say you've already collected your interest for the day (even if you haven't).

It is supposed to be that way. It used to not be that way, but a few users were abusing this feature and it got changed about a year ago.

Really? How would you abuse that?

People were passing around large amount of sP to get the interest each day.

Locking this since it is not a bug.