I have had a number of "Error saving results" emails for one of my surveys.
The relevant error portion is:
SQL CODE THAT FAILED:
UPDATE {{survey_616355}} SET `lastpage`=0, `datestamp`='2018-04-18 07:38:09', ``=NULL WHERE ID=324
ERROR MESSAGE:
And there is no error message -- although looking at the SQL I see there is a missing field before the =NULL -- it's blank ... I'd imagine that a field name should be within the quotes.