Random "Permission denied" errors on macOS ARM64

We try to compile e.g. ounit2 but get random errors on macOS ARM64, all works fine on e.g. macOS x86-64 or Linux/Windows.

Expected Behavior

Compile works.

Actual Behavior

Random compile errors with

Running[55]: (cd _build/default && /makefactory/usr/20210413/191623/debug/macos64/bin/ocamlc.opt -w @1..3@5..28@30..39@43@46..47@49..57@61..62-40 -strict-sequence -strict-formats -short-paths -keep-locs -g -bin-annot -I src/lib/ounit2/advanced/.oUnitAdvanced.objs/byte -I /makefactory/usr/20210413/191623/debug/macos64/lib/ocaml/bytes -I /makefactory/usr/20210413/191623/debug/macos64/lib/ocaml/stdlib-shims -no-alias-deps -opaque -o src/lib/ounit2/advanced/.oUnitAdvanced.objs/byte/oUnitRunnerProcesses.cmo -c -impl src/lib/ounit2/advanced/oUnitRunnerProcesses.ml)
Error: Permission denied

This is the output with

'dune' 'build' '-j2' '--profile=dev' '--display=verbose' '-p' 'ounit2'

Reproduction

Unfortunately that is very sporadic.
After a compile failed, this error is persistent in the same compile tree/build dir.

Specifications

I use OCaml 4.12.0 and dune 2.8.5 on macOS ARM64.
Latest macOS release on ARM64 with all patches.

Start by running the reported dune build command with -j2 and verbose display on macOS ARM64, focusing on compilation of src/lib/ounit2/advanced/oUnitRunnerProcesses.ml. Compare a failed build tree with successful builds and inspect the reported Permission denied path. Done means identifying the cause of the sporadic failure and making the compile complete reliably.