I've had some reports of the following behavior in a 2.10 install. On submission of a (fairly long---14 problem) gateway/quiz assignment, there is an error page with a mysql error:
DBD::mysql::st execute failed: Got a packet bigger than 'max_allowed_packet' bytes at /.../webwork2/lib/WeBWorK/DB/Schema/NewSQL/Std.pm line 826.
Attempting to reenter the test elicits the error
Can't use an undefined value as an ARRAY reference at /.../webwork2/lib/WeBWorK/Utils.pm line 871.
This is in decodeAnswers().
I changed the max_packet_size in the my.cnf file to 16MB, which caused the assignment to function fine for another submission or two before triggering the same error.
To me this suggests that somewhere in the answer handling (maybe the past answers table) there's an issue with the size of the dataset that is being retrieved. I haven't looked at this carefully however.
Any thoughts would be very welcome!