Expression.Error: There weren't enough elements in the enumeration to complete the operation

[Seaweed81]

I know this has been asked before however, none of the "solved" seems to fit.  I get this error when I refresh sometimes 20 times, sometimes just once and sometimes it works right away.  I guess my confusion is it will just eventaully work and sometimes on the 1st time.  Any idea what would cause this?  I'm new to this as most of this was built for me, and I'm trying to learn it, but this one has the best of me and is beyond frustrating.