Dear Koha Community Following up my post on 12 June I am repeating my call for help as Koha is effectively unusable right now at one of our libraries. We are running Koha 19.11 on Debian 9.11 (stretch). This supports 5 Koha instances for some of the volunteer-run libraries in Sheffield. It has been stable and working fine for many months. Currently we have a serious problem with one of these instances. Any attempt to check out a book hangs (never completes) and we see /usr/share/koha/intranet/cgi-bin/circ/circulation.pl consuming most of the CPU cycles (stuck in a loop perhaps?). On one occasion I noticed it was renew.pl consuming all the CPU. I have tried disabling plack for this instance, and have rebuilt the zebra index, but the problem persists. There is nothing obvious reported in the log files, though I may not be looking in the right places. I cannot see any obvious problems with the configuration, though again I might be looking at the wrong things. The other 4 instances are working OK. *Any advice on how to debug or fix this would be greatly appreciated.* Does anyone know how to turn on tracing of MySQL transactions? I was wondering if looking at the activity at the database end might help. Thanks and Best Regards, Chris Brown (Voluntary Libraries in Sheffield)