Error using frankv with random ties method

[rbutleriii]

When trying to use frankv to assign group based rankings, I got a confusing error. The issue seems to be only with the ties.method="random"

Example:

dt1 = data.table(id=c('11', '11', '11', '22', '22', '88', '99', '44', '44', '55'),
                 id2=c('11', '12', '12', '23', '23', '89', '90', '45', '45', '56'),
                 id3=c('11', '13', '13', '23', '23', '89', '91', '46', '46', '57'),
                 id4=c('11', '14', '14', '24', '24', '80', '92', '47', '47', '58'),
                 date = as.Date(c("01-01-2016", "01-02-2016", "01-02-2016", "02-01-2016",
                                  "02-02-2016"), format = "%m-%d-%Y"))
colz = c("id", "id4", "id3", "id2")
dt1[, rank := frankv(.SD, cols=colz, order=-1L, ties.method="first"), by="date"]
dt1[, rank := frankv(.SD, cols=colz, order=-1L, ties.method="last"), by="date"]
dt1[, rank := frankv(.SD, cols=colz, order=-1L, ties.method="average"), by="date"]
dt1[, rank := frankv(.SD, cols=colz, order=-1L, ties.method="max"), by="date"]
dt1[, rank := frankv(.SD, cols=colz, order=-1L, ties.method="min"), by="date"]
dt1[, rank := frankv(.SD, cols=colz, order=-1L, ties.method="dense"), by="date"]
dt1[, rank := frankv(.SD, cols=colz, order=-1L, ties.method="random"), by="date"]
# Error in set(x, idx, "..stats_runif..", stats::runif(n)) :
#   .SD is locked. Updating .SD by reference using := or set are reserved for future use. Use := in j directly. 
# Or use copy(.SD) as a (slow) last resort, until shallow() is exported.

[ben-schwen]

I cannot reproduce on the current dev version. Which system and data.table version are you using? (Output of sessionInfo()).

Duplicate to #4434 resp. #4429. Feel free to reopen if I'm in error assigning the duplicate label.