A known issue, just VPP Jira ticket was missing.

Affects tests with large packet sizes and low number of crypto workers.
Symptoms are varied: Reduced performance, zero performance, performance decreasing down to zero.

For more details see the three places this issue was discussed before:
Gerrit: https://gerrit.fd.io/r/c/vpp/+/30386
Csit-dev mailer: https://lists.fd.io/g/csit-dev/topic/85838822#4412
CSIT Jira ticket: https://jira.fd.io/browse/CSIT-1780