I was updating Guix today with the option rounds=2 and I hit an error with mpv having different outputs everytime it was built.
The message is this:
\output ‘/gnu/store/q71zaxglbwmw3z4r1a3jmf1mgwrpmv4c-mpv-0.32.0’ of ‘/gnu/store/qkmylc2cd950kf4zk8y3ay0hpwcvjpvr-mpv-0.32.0.drv’ differs from previous round
build of /gnu/store/qkmylc2cd950kf4zk8y3ay0hpwcvjpvr-mpv-0.32.0.drv failed
View build log at '/var/log/guix/drvs/qk/mylc2cd950kf4zk8y3ay0hpwcvjpvr-mpv-0.32.0.drv.bz2'.
cannot build derivation `/gnu/store/3j9pkj5kad042i1zyqzdw2vl1yfsbznk-celluloid-0.19.drv': 1 dependencies couldn't be built
guix upgrade: error: build of `/gnu/store/3j9pkj5kad042i1zyqzdw2vl1yfsbznk-celluloid-0.19.drv' failed
And my system is this:
Generation 9 Jun 23 2020 19:41:06 (current)
Let me know if there is more information I can provide.