This call was failing since SCHED_FIFO doesn't support negative priorities, but only positive ones, see third paragraph of scheduling policies: https://man7.org/linux/man-pages/man7/sched.7.html.
Additionally Linux do provice up to 99 levels, but I've limited myself to the required UNIX standard of 32, and split the priority levels evenly from that.
I've also added a couple of rows to debug additional issues in the future like this.
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