HP V1910-48G switch ports of aggregation group become INACTIVE

[aa4]

On our V1910 switch we have observed intermittent network disconnections.

Based on the log file, the ports with the highest number of network disconnections (indicated with "link status is DOWN") were 4 ports (Ports 9, 30, 31, 32) that are members of a static aggregation group identified as BAGG9.
In the logfile, the following message is recorded for Port 9 (Similar messages appear for ports 30,31,32):
"Port member GigabitEthernet1/0/9 of aggregation group BAGG9 becomes INACTIVE, because the port's configuration is improper for aggregation."

We have checked our configuration and found that the 4 ports have the following settings:
•802.1X protocol is disabled
•Handshake is enabled
•Periodic reauthentication is disabled
•The port is an authenticator
•Authentication Mode is Auto
•Port Control Type is Mac-based
•802.1X Multicast-trigger is enabled
•Mandatory authentication domain: NOT configured
•Guest VLAN: NOT configured
•Auth-Fail VLAN: NOT configured
•Max number of on-line users is 256

Which of these settings is "improper for aggregation"?