I managed to reduce it to this patch, now applied to git as 1050-armel-atomic-past-buffer.patch. No idea why it help, but worked when doing test build on armel / abel.debian.org.
--- tbb.orig/src/tbb/concurrent_monitor.h 2023-07-30 20:28:22.251868539 +0000 +++ tbb/src/tbb/concurrent_monitor.h 2023-07-31 06:47:43.046714530 +0000 @@ -290,7 +290,10 @@ n = my_waitset.front(); if (n != end) { my_waitset.remove(*n); - to_wait_node(n)->my_is_in_list.store(false, std::memory_order_relaxed); + wait_node<Context>* wn = to_wait_node(n); + if (wn) { + wn->my_is_in_list.store(false, std::memory_order_relaxed); + } } } -- Happy hacking Petter Reinholdtsen