Danny Milosavljevic <dannym@scratchpost.org> writes:

> $ guix build texlive-texmf-minimal --rounds=2
>
> phase `texmf-config' succeeded after 52.0 seconds
> output ‘/gnu/store/jfs5fsn011w64jgmpc6chcnqr1agfv6h-texlive-texmf-minimal-2016’ of ‘/gnu/store/72z7v217vd976hlhyjrxzmwpqr4nzwh6-texlive-texmf-minimal-2016.drv’ differs from ‘/gnu/store/jfs5fsn011w64jgmpc6chcnqr1agfv6h-texlive-texmf-minimal-2016-check’ from previous round
> @ build-failed /gnu/store/72z7v217vd976hlhyjrxzmwpqr4nzwh6-texlive-texmf-minimal-2016.drv - 1 output ‘/gnu/store/jfs5fsn011w64jgmpc6chcnqr1agfv6h-texlive-texmf-minimal-2016’ of ‘/gnu/store/72z7v217vd976hlhyjrxzmwpqr4nzwh6-texlive-texmf-minimal-2016.drv’ differs from ‘/gnu/store/jfs5fsn011w64jgmpc6chcnqr1agfv6h-texlive-texmf-minimal-2016-check’ from previous round
> note: keeping build directory `/tmp/guix-build-texlive-texmf-minimal-2016.drv-0'
> cannot build derivation `/gnu/store/dpnlwahp8gp65s6a2q3808z9dgcx0cxj-texlive-minimal-2016.drv': 1 dependencies couldn't be built

Can you try building with -K and then run:

$ diffoscope /gnu/store/... /gnu/store/...-check | tee diff.out

Please attach a compressed "diff.out" here.