Just to check in, I've still been seeing this fairly consistently. Hoping someone can suggest some further debugging steps.
Today the message seems slightly different: [2019-01-14 12:06:24.690252594] main: starting assistant version 7.20181211 git-annex: internal error: evacuate: strange closure type 4325407 (GHC version 8.4.4 for x86_64_unknown_linux) Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug so the number has changed from 4325404 to 4325407. Not sure if that means anything.