These kind of errors happen again:

$ guix system build /etc/config.scm
/etc/config.scm:233:14: waarschuwing: the 'target' field is deprecated, 
please use 'targets' instead
substitute: lijst van substituten van ‘https://ci.guix.gnu.org’ aan het 
bijwerken... 100.0%
substitute: lijst van substituten van ‘https://bordeaux.guix.gnu.org’ 
aan het bijwerken... 100.0%
substitute: lijst van substituten van ‘https://substitutes.nonguix.org’ 
aan het bijwerken... 100.0%
The following derivations will be built:
   /gnu/store/f0s8dnja8qli9qclpprlkj43nma54pm2-system.drv
   /gnu/store/2qlkyj3cgbfykqg3frqmyadq8k2brckn-boot.drv
   /gnu/store/mcilwp3nrjh8sg6fw98xs2j1bk3s5da4-shepherd.conf.drv
   /gnu/store/023jq2rnz9ilww080676qwnl2arz2q80-shepherd-cups.go.drv
   /gnu/store/7kgzwyy4rajwdkm6qgb11asgpqxb2pfw-shepherd-cups.scm.drv
/gnu/store/7kgzwyy4rajwdkm6qgb11asgpqxb2pfw-shepherd-cups.scm.drv bouwen...
/gnu/store/7kgzwyy4rajwdkm6qgb11asgpqxb2pfw-shepherd-cups.scm.drv 
succesvol gebouwd
/gnu/store/023jq2rnz9ilww080676qwnl2arz2q80-shepherd-cups.go.drv bouwen...
;;; WARNING: loading compiled file 
/gnu/store/4nw0zb4swga0cb8i35nvng3rg6z5qm8p-shepherd-0.9.3/lib/guile/3.0/site-ccache/shepherd/service.go 
failed:
;;; In procedure load-thunk-from-memory: incompatible bytecode version
;;; WARNING: loading compiled file 
/gnu/store/4nw0zb4swga0cb8i35nvng3rg6z5qm8p-shepherd-0.9.3/lib/guile/3.0/site-ccache/shepherd/support.go 
failed:
;;; In procedure load-thunk-from-memory: incompatible bytecode version
;;; WARNING: loading compiled file 
/gnu/store/4nw0zb4swga0cb8i35nvng3rg6z5qm8p-shepherd-0.9.3/lib/guile/3.0/site-ccache/shepherd/config.go 
failed:
;;; In procedure load-thunk-from-memory: incompatible bytecode version
;;; WARNING: loading compiled file 
/gnu/store/4nw0zb4swga0cb8i35nvng3rg6z5qm8p-shepherd-0.9.3/lib/guile/3.0/site-ccache/shepherd/comm.go 
failed:
;;; In procedure load-thunk-from-memory: incompatible bytecode version
;;; WARNING: loading compiled file 
/gnu/store/4nw0zb4swga0cb8i35nvng3rg6z5qm8p-shepherd-0.9.3/lib/guile/3.0/site-ccache/shepherd/system.go 
failed:
;;; In procedure load-thunk-from-memory: incompatible bytecode version
/gnu/store/023jq2rnz9ilww080676qwnl2arz2q80-shepherd-cups.go.drv 
succesvol gebouwd
/gnu/store/mcilwp3nrjh8sg6fw98xs2j1bk3s5da4-shepherd.conf.drv bouwen...
/gnu/store/mcilwp3nrjh8sg6fw98xs2j1bk3s5da4-shepherd.conf.drv succesvol 
gebouwd
/gnu/store/2qlkyj3cgbfykqg3frqmyadq8k2brckn-boot.drv bouwen...
/gnu/store/2qlkyj3cgbfykqg3frqmyadq8k2brckn-boot.drv succesvol gebouwd
/gnu/store/f0s8dnja8qli9qclpprlkj43nma54pm2-system.drv bouwen...
/gnu/store/f0s8dnja8qli9qclpprlkj43nma54pm2-system.drv succesvol gebouwd
/gnu/store/fw1da6r6y4f1k8ddrfq4rr5xlgm9gzsc-system

Greetings,
Maxime.