Coarray Fortran segfaults when passing distributed argument

Question

I am getting a segfault in C = C + matmul(A(:, 1 + (l - 1) * n / p: l * n / p), B(:,:)[l]) using gfortran + mpich, with n = 4000, p = 2. Is it not allowed to pass slices of distributed arrays into functions? When copying out B(:,:)[l], it is super slow, and I get a "unexpected tag-receive descriptor 0x561965b27900 was not matched"-error (though after the program finishes).

program main
    implicit none

    integer :: n, p, l
    real(KIND=8), allocatable :: A(:,:)[:], B(:,:)[:], C(:,:)[:]
    character(len=12), dimension(:), allocatable :: args
    integer :: cpu_count, cpu_count2, count_rate, count_max

    allocate(args(1))
    call get_command_argument(1, args(1))
    read (unit=args(1),fmt=*) n

    p = num_images()

    if (modulo(n, p) /= 0) then
        write (*, *) 'Please make sure n divides p'
    end if

    allocate(A(n / p, n)[*])
    allocate(B(n / p, n)[*])
    allocate(C(n / p, n)[*])

    A = 1
    B = 1
    C = 0

    sync all
    call system_clock(cpu_count, count_rate, count_max)

    do l = 1, num_images()
        C = C + matmul(A(:, 1 + (l - 1) * n / p: l * n / p), B(:,:)[l])
    end do

    sync all
    call system_clock(cpu_count2, count_rate, count_max)

    if (this_image() .eq. 1) then
        write (*, *) 2.0 * n * n * n / (real(cpu_count2 - cpu_count) / &
                    count_rate) / 1000000000.0
    end if
end program main