Did you receive an answer to this or figure it out? Having the same issue suddenly in the last few weeks. Portal updated file before that.
No, still no resolution to this. I Have a different file that is set up the same and it works ok.
The one that doesnt work still wont update totals unless you click in the field or move records.
Haven't looked back at this yet as been doing other things but will have to shortly.
I'll reply if i find anything.