filterAndTrim returns error " 'names' attribute [81] must be the same length as the vector [33]" although fnFs, filtFs, fnRs and filtRs have the same length

[jorgeamaya]

I'm running DADA2 version 1.20.0. I'm encountering the following error upon reaching filterAndTrim()

Error in names(answer) <- names1 : 
  'names' attribute [81] must be the same length as the vector [33]
Calls: filterAndTrim -> mcmapply
In addition: Warning message:
In mclapply(seq_len(n), do_one, mc.preschedule = mc.preschedule,  :
  scheduled cores 2, 4, 5, 6, 8, 9, 11 did not deliver results, all values of the jobs will be affected
Execution halted

I verified that fnFs, filtFs, fnRs and filtRs have the same length (81 files) and they do. Interestingly, the program runs ok with certain subsets of files. So I ran the program and progressively removed files until I found an offending file. If run this file individually, it runs ok. Thus, I don't know for sure what is inside this file that is offending to the program. Has this error occurred before? If so, how to approach it?