rca: 
   test: 100b tcp tput
   frequency: all
   testbed: 2n-clx, 2n-icx, 2n-skx

example:

https://s3-logs.fd.io/vex-yul-rot-jenkins-1/csit-vpp-perf-report-iterative-2206-2n-clx/13/log.html.gz#s1-s1-s1-s2-s38-t1

https://s3-logs.fd.io/vex-yul-rot-jenkins-1/csit-vpp-perf-report-iterative-2206-2n-icx/2/log.html.gz#s1-s1-s1-s2-s15-t1

https://s3-logs.fd.io/vex-yul-rot-jenkins-1/csit-vpp-perf-report-iterative-2206-2n-skx/2/log.html.gz#s1-s1-s1-s2-s17-t1

This is with TRex v2.97 (and using reset).
Does not affect UDP tests.
Does not happen on 2n-dnv, does happen on 2n-skx and 2n-clx.
The error happens on client.stop() call (with or without block=False) so it affects both synchronous and asynchronous stop, but the exact symptom looks different.
Transaction scale does not seem to matter.

More investigations are in progress.