Submission failure with multicore cluster functions

[cfhammill]

I'm getting a strange error when running some tests for my package with rocker/r-devel

Creating dir: //qMincApply_registry
Saving registry: //qMincApply_registry/registry.RData
Range: 4.000000 1.000000
Adding 4 jobs to DB.
Saving conf: //qMincApply_registry/conf.RData
Submitting 4 chunks / 4 jobs.
Cluster functions: Multicore.
Auto-mailer settings: start=none, done=none, error=none.
Warning in as.list(as.numeric(stri_split_regex(res, "\\s+")[[1L]])) :
  NAs introduced by coercion
Error in if (worker$status$n.jobs >= worker$max.jobs) return("J") : 
  missing value where TRUE/FALSE needed
Sending 0 submit messages...
Might take some time, do not interrupt this!
Syncing registry ...

The config I'm using is:

setConfig(list(cluster.functions = 
  makeClusterFunctionsMulticore(max.jobs = min(2, parallel::detectCores() - 1))))

This issue does not occur with interactive cluster functions. This code runs fine with R 3.3.1.