Hello,
The SCTP ALG checks the source port number, destination port number and verification tag of a packet for an anomaly (deviation from normal behavior). Abnormal SCTP packets will be dropped by the SCTP ALG.The SCTP ALG does not check the payload for an anomaly. As such, in this case, it looks like the issue was with the tag that the traffic was coming in as pointedout previously.
Regards
Vatsa