It has been a few months, and we still experience the issue. Today, we started an experiment updating one of the computers to the following newer packages: libnftables1_1.0.6-2_amd64.deb libnftnl11_1.2.4-2_amd64.deb nftables_1.0.6-2_amd64.deb python3-nftables_1.0.6-2_amd64.deb, compiled from source because the pre-built binaries from debian unstable repositories depend on an incompatible libc6. I'll let this run for a few weeks to see if it resolves the segfault issue.
If it does not help, I could try Bernhard's suggestion of rr-debugger. Greetings, Tjeu
