Comment 7 for bug 1911400

And in my tests with further debug-modification the the stacktrace isn't helpful - so still no insight where to look at.

Also my communication with upstream/community on IRC didn't bring up a new approach to this.

To be sure I also ran things on canonistack instances - finally - there on arm64 it triggered.

[inst/parcellfun.m]
>>>>> /home/ubuntu/octave-parallel-4.0.0/inst/parcellfun.m
***** test
 assert (res = parcellfun (3, @ (x, y) x * y, {1, 2, 3, 4}, {2, 3, 4, 5}), [2, 6, 12, 20])
***** test
 assert (res = parcellfun (4, @ (x, y) x * y, {1, 2, 3, 4}, {2, 3, 4, 5}, "UniformOutput", false), {2, 6, 12, 20})
***** test
 assert (res = parcellfun (2, @ (x, y) x * y, {1, 2, 3, 4}, {2, 3, 4, 5}, "ChunksPerProc", 2), [2, 6, 12, 20])
***** test
 assert (res = parcellfun (4, @ (x, y) x * y, {1, 2, 3, 4}, {2, 3, 4, 5}, "CumFunc", @ (a, b) a + b), 40)
***** test
 assert (res = parcellfun (2, @ (x, y) x * y, {1, 2, 3, 4}, {2, 3, 4, 5}, "ChunksPerProc", 2, "CumFunc", @ (a, b) a + b), 40)
!!!!! test failed
int32 scalar cannot be indexed with {
***** test
 assert (ischar ((res = parcellfun (4, @ (x) sqrt (x), {1, "a", 3, 4, 5, 6},
                                    "ErrorHandler",
                                    @ (info, x) info.message,
                                    "UniformOutput", false)){2}))
6 tests, 5 passed, 0 known failure, 0 skipped
[inst/pararrayfun.m]

Hopefully that allows more debugging now.