Too many jobs causes "BatchtoolsExpiration: Future ('<none>') expired"

Whenever I run approx. > 200 jobs on our SGE cluster, I get the following error:

BatchtoolsExpiration: Future ('<none>') expired (registry path /ebio/abt3_projects/software/dev/DeepMAsED/notebooks/04_contig_viewing/.future/20190812_101254-P53iu9/batchtools_2061698801)

If I manually batch the jobs into smaller groups (eg., 50 or 100 jobs), then I don't get this error.

Version: r-batchtools 0.9.11 r341hc070d10_0 conda-forge

~/.batchtools.conf.R file:

default.resources = list(h_rt = '00:59:00',
                         h_vmem = '4G',
			 threads = '1',
                         conda.env = 'py3')
cluster.functions = makeClusterFunctionsSGE(template = "~/.batchtools.tmpl")
temp.dir = "/ebio/abt3_projects/temp_data/"

.batchtools.tmpl file:

#!/bin/bash
#$ -N <%= job.name %
#$ -j y
#$ -o <%= log.file %>
#$ -cwd
#$ -V
#$ -pe parallel <%= resources$threads %>
#$ -l h_rt=<%= resources$h_rt %>
#$ -l h_vmem=<%= resources$h_vmem %>


. ~/.bashrc
conda activate <%= resources$conda.env %>

## Export value of DEBUGME environemnt var to slave
export DEBUGME=<%= Sys.getenv("DEBUGME") %>

<%= sprintf("export OMP_NUM_THREADS=%i", resources$omp.threads) -%>
<%= sprintf("export OPENBLAS_NUM_THREADS=%i", resources$blas.threads) -%>
<%= sprintf("export MKL_NUM_THREADS=%i", resources$blas.threads) -%>

Rscript -e 'batchtools::doJobCollection("<%= uri %>")'
exit 0

Example of resources used:

resources = list(h_rt = '00:59:00',
                 h_vmem = '4G',
                 threads = 1,
                 conda.env = 'py3_batchtools')     # conda env with batchtools installed
plan(batchtools_sge, resources=resources, workers=50)

I'm using future_lapply() to run a function that calls system2()

Start by reproducing the failure with future_lapply(), system2(), and more than 200 jobs using the shown SGE configuration. Read ~/.batchtools.conf.R and .batchtools.tmpl, then inspect how plan(batchtools_sge, workers=50) submits and tracks job collections. Done means the workload completes without BatchtoolsExpiration while preserving the reported resource settings.