An error was encountered while running DADA2 in R (return code 1); Error in err[c(1, 6, 11, 16), ] <- 1

[thermokarst]

I believe the error is stemming from an issue related to the characteristics of the reads (I seem to recall this has to do with the case when many (all?) sequences are unique). See this thread for more detail:

Error running DADA2 in 454 data

I found a similar error on the DADA2 error tracker: Maybe you can try some of the checks suggested in that thread? You will already have a copy of DADA2 (and R) on hand in your QIIME 2 env. FWIW, in the linked issue it sounds like the reason this error happened is because all of the reads in the data were unique - no groupings of reads were identified.