On current master (commit af184b68e78aa51b6ff50b7327dfbbdb1d6e6843), deeptools does not build reproducibly:
$ guix build --check --no-grafts deeptools --8<---------------cut here---------------start------------->8--- ... guix build: error: derivation `/gnu/store/hky07zjsvai0x3n99lqmgyh6rhld6v4s-deeptools-3.1.3.drv' may not be deterministic: output `/gnu/store/0j8200f20mp5grjkjh5kw2q9a67gw3rn-deeptools-3.1.3' differs --8<---------------cut here---------------end--------------->8--- $ diff -ru "$(guix build deeptools)" /gnu/store/0j8200f20mp5grjkjh5kw2q9a67gw3rn-deeptools-3.1.3 --8<---------------cut here---------------start------------->8--- │ │ │ │ ├── tree.cpython-37m-x86_64-linux-gnu.so │ │ │ │ │ ├── /gnu/store/02iklp4swqs0ipxhg5x9b2shmj6b30h1-binutils-2.31.1/bin/readelf --wide --dynamic {} │ │ │ │ │ │ @@ -2,15 +2,15 @@ │ │ │ │ │ │ Dynamic section at offset 0xcd90 contains 30 entries: │ │ │ │ │ │ Tag Type Name/Value │ │ │ │ │ │ 0x0000000000000001 (NEEDED) Shared library: [libz.so.1] │ │ │ │ │ │ 0x0000000000000001 (NEEDED) Shared library: [libpython3.7m.so.1.0] │ │ │ │ │ │ 0x0000000000000001 (NEEDED) Shared library: [libgcc_s.so.1] │ │ │ │ │ │ 0x0000000000000001 (NEEDED) Shared library: [libpthread.so.0] │ │ │ │ │ │ 0x0000000000000001 (NEEDED) Shared library: [libc.so.6] │ │ │ │ │ │ - 0x000000000000001d (RUNPATH) Library runpath: [/gnu/store/9z98cvjm7p7z21xdid1ryydxy5vyz6wr-python-3.7.0/lib:/gnu/store/h90vnqw0nwd0hhm1l5dgxsdrigddfmq4-glibc-2.28/lib:/gnu/store/4sqps8dczv3g7rwbdibfz6rf5jlk7w90-gcc-5.5.0-lib/lib:/gnu/store/nq4lsyipmfb0q7g26ra45rwwqrh3x8zw-zlib-1.2.11/lib:/gnu/store/4sqps8dczv3g7rwbdibfz6rf5jlk7w90-gcc-5.5.0-lib/lib/gcc/x86_64-unknown-linux-gnu/5.5.0/../../..] │ │ │ │ │ │ + 0x000000000000001d (RUNPATH) Library runpath: [/gnu/store/b7fqhszxl02g6pfm3vw6b3cjz472qrly-python-3.7.0/lib:/gnu/store/h90vnqw0nwd0hhm1l5dgxsdrigddfmq4-glibc-2.28/lib:/gnu/store/4sqps8dczv3g7rwbdibfz6rf5jlk7w90-gcc-5.5.0-lib/lib:/gnu/store/nq4lsyipmfb0q7g26ra45rwwqrh3x8zw-zlib-1.2.11/lib:/gnu/store/4sqps8dczv3g7rwbdibfz6rf5jlk7w90-gcc-5.5.0-lib/lib/gcc/x86_64-unknown-linux-gnu/5.5.0/../../..] --8<---------------cut here---------------end--------------->8--- There are multiple more instances of differences in the two versions. Maybe something to do with two flavors of Python being used? $ guix refresh --list-transitive deeptools | tr ' ' '\n' | grep -E 'python-(minimal|wrapper)|python2?@' python@3.7.0 python@3.7.0 python-wrapper@3.7.0 python-minimal@3.7.0 python-minimal-wrapper@3.7.0 python2@2.7.15