iRule [after 8000] causing TMM reset

Just check the big tracker with maybe "irule after" or the release notes for your version:

https://support.f5.com/csp/bug-tracker

https://techdocs.f5.com/kb/en-us/products/big-ip_ltm/releasenotes/related/relnote-supplement-bigip-12-1-6.html

Also see the ltm/kern/tmm logs about the error and if you can google it as this may help and the logs may also show if the CPU and memory/SWAP had issues because of the "after 8000" command. Here is a helpfull article that I did a long time ago:

https://community.f5.com/t5/crowdsrc/knowledge-sharing-investigating-troubleshooting-crash-and/ta-p/297501