slow-validate failure: memo001 assertion failure in rts/sm/Sanity.c

Reproduce with

hadrian/build test --freeze1  --docs=none --flavour=slow-validate --test-speed=slow --only="memo001"

There is an assertion failure in rts/sm/Sanity.c.

The assertion in question is:

ASSERT(countNonMovingHeap(&nonmovingHeap) == gen->n_blocks); 

Wrong exit code for memo001(nonmoving_thr_sanity)(expected 0 , actual 134 )
Stderr ( memo001 ):
memo001: internal error: ASSERTION FAILED: file rts/sm/Sanity.c, line 1123

Stack trace:
                  0x84790f    set_initial_registers (rts/Libdw.c:294.57)
            0x7f4bcf423fa8    dwfl_thread_getframes (/nix/store/fqklswrymlx110vj0sfmpq77yj99paiz-elfutils-0.186/lib/libdw-0.186.so)
            0x7f4bcf423aeb    get_one_thread_cb (/nix/store/fqklswrymlx110vj0sfmpq77yj99paiz-elfutils-0.186/lib/libdw-0.186.so)
            0x7f4bcf423e12    dwfl_getthreads (/nix/store/fqklswrymlx110vj0sfmpq77yj99paiz-elfutils-0.186/lib/libdw-0.186.so)
            0x7f4bcf424357    dwfl_getthread_frames (/nix/store/fqklswrymlx110vj0sfmpq77yj99paiz-elfutils-0.186/lib/libdw-0.186.so)
                  0x8477f9    libdwGetBacktrace (rts/Libdw.c:263.15)
                  0x7f3983    rtsFatalInternalErrorFn (rts/RtsMessages.c:175.30)
                  0x7f3542    barf (rts/RtsMessages.c:49.4)
                  0x7f35a5    errorBelch (rts/RtsMessages.c:68.5)
                  0x82295b    genBlocks (rts/sm/Sanity.c:1124.9)
                  0x822eb9    memInventory (rts/sm/Sanity.c:1211.46)
                  0x812fa0    GarbageCollect (rts/sm/GC.c:1087.3)
                  0x7fb6d3    scheduleDoGC (rts/Schedule.c:1861.5)
                  0x7f9739    schedule (rts/Schedule.c:580.21)
                  0x7fc97c    scheduleWaitThread (rts/Schedule.c:2634.5)
                  0x7eefb1    rts_evalLazyIO (rts/RtsAPI.c:563.5)
                  0x7f33ee    hs_main (rts/RtsMain.c:73.9)
                  0x409a67    (null) (/run/user/1000/ghctest-derda1up/test   spaces/libraries/base/tests/memo001.run/memo001)
            0x7f4bcf4c01d7    __libc_start_call_main (/nix/store/ybkkrhdwdj227kr20vk8qnzqnmj7a06x-glibc-2.34-115/lib/libc.so.6)
            0x7f4bcf4c0297    __libc_start_main@@GLIBC_2.34 (/nix/store/ybkkrhdwdj227kr20vk8qnzqnmj7a06x-glibc-2.34-115/lib/libc.so.6)
                  0x406471    _start (../sysdeps/x86_64/start.S:118.0)

    (GHC version 9.5.20220805 for x86_64_unknown_linux)
    Please report this as a GHC bug:  https://www.haskell.org/ghc/reportabug
*** unexpected failure for memo001(nonmoving_thr_sanity)