R "mi" package: mi(...) command throws error - r

Question

I am attempting to do multiple imputation with the "mi" package (v1.0). Due to computing/processing time constraints, I split my code into two files. The first does all of the mi-style preprocessing, and the second actually runs the imputation.
The first file runs without error, but I am including it here for completeness (below is an edited, shorter version of the file):
require(mi)
# Load data for multiple imputation
data = as.data.frame(read.delim("for_mi.csv"))
...
# Declare data as missing data frame for MI functions
mdf = missing_data.frame(data)
mdf <- change(mdf, y = "x", what = "type", to = "nonnegative-continuous")
... (many type corrections later) ...
mdf <- change(mdf, y = "y", what = "type", to = "positive-continuous")
# Save pre-processed missing-format data for analysis in r_mi_2.R.
saveRDS(mdf,"preprocessed.rds")
The second file is the one that throws the error:
require(mi)
# Load output from first file
mdf <- readRDS("preprocessed.rds")
# Note: at this point, mdf loads as a missing_data.frame.
# MI commands such as show(mdf) function as expected.
# Impute data
imputations <- mi(mdf, n.iter = 30, n.chains = 4, max.minutes = Inf, parallel = TRUE)
I get the following output:
Chain 1
Chain 1 Iteration 0
Chain 2
Chain 2 Iteration 0
Chain 1 Iteration 1
Chain 3
Chain 3 Iteration 0
Chain 2 Iteration 1
Chain 4
Chain 4 Iteration 0
Chain 3 Iteration 1
Chain 4 Iteration 1
Error in checkForRemoteErrors(val) :
4 nodes produced errors; first error: cannot open the connection
Calls: mi ... clusterApply -> staticClusterApply -> checkForRemoteErrors
Warning message:
In file(file, ifelse(append, "a", "w")) :
cannot open file '/var/tmp/Rtmp0TqkWn/mi1502972500/pars_1.csv': No such file or directory
Warning message:
In file(file, ifelse(append, "a", "w")) :
cannot open file '/var/tmp/Rtmp0TqkWn/mi1502972500/pars_2.csv': No such file or directory
Execution halted
Warning message:
In file(file, ifelse(append, "a", "w")) :
cannot open file '/var/tmp/Rtmp0TqkWn/mi1502972500/pars_3.csv': No such file or directory
Warning message:
In file(file, ifelse(append, "a", "w")) :
cannot open file '/var/tmp/Rtmp0TqkWn/mi1502972500/pars_4.csv': No such file or directory
Other background info:
I am running the code on a cluster, using 8 processors on a single node. I have also tried running it locally on my computer, with the same result.
I have tried varying the number of chains, lowering the number of iterations, and setting parallel = FALSE, all to no avail.
I have tried running the code with and without the options(mc.cores = 4) line that appears in the mi vignette (see here, page 4)
The mi vignette linked above states that many errors from running mi stem from running out of RAM. I'm not sure how to test this, but some info: the starting object mdf is 128MB, the per-user server cap on the cluster is 32GB, and the error throws even if I set parallel=FALSE or n.iter=1.
Any help would be greatly appreciated. Thank you!
Edit: The error output with parallel = FALSE is:
Chain 1
Chain 1 Iteration 0
Chain 1 Iteration 1
Error in file(file, ifelse(append, "a", "w")) :
cannot open the connection
Calls: mi -> mi -> .local -> .mi -> write.table -> file
In addition: Warning message:
In file(file, ifelse(append, "a", "w")) :
cannot open file '/var/tmp/Rtmp0TqkWn/mi1502972500/pars_1.csv': No such file or directory
Execution halted