The best thing which could be done is to post a set of SQL queries on this list which allows to reproduce the problem.
I am trying, but I am not sure how to do that just yet. However, I can reliably reproduce the error by letting this system run, meaning I have the ability to attach a debugger to see what is happening more deeply. I can also provide just what data in the slot is leading to a failed assert. Would any of this help to narrow down the problem?