This is not seen in CSIT under usual conditions.
But it somewhat frequently happens with a new (unmerged) CSIT code [0] tested on 2n-icx testbed. (Daily job [2] usually passes there without any failures.)
That code should not do anything specific for AVF, but it switches Python API client to async mode, so messages may be arriving (over socket) somewhat differently (not sure how differently yet).
Either way, VPP should not occasionally crash in avf_process_request [1] just because something is different on API level.

[0] https://gerrit.fd.io/r/c/csit/+/36774
[1] https://s3-logs.fd.io/vex-yul-rot-jenkins-1/csit-vpp-perf-verify-master-2n-icx/35/log.html.gz#s1-s1-s1-s1-s1-t1-k3-k4-k1
[2] https://jenkins.fd.io/view/csit/job/csit-vpp-perf-mrr-daily-master-2n-icx/