This problem has been persistent for a while, just happens every so often at random times, nothing changing. I also do not know how to reproduce the problem, but I\'ll give a de
I had the same problem and solved it by using
=IF(ISERROR(A1);IMPORTRANGE();IMPORTRANGE())
in the cell where earlier IMPORTRANGE used to be and by turning on Iterative calculation in spreadsheet’s location & calculation settings.
Hope it help someone