R Error in env_has(env, var, inherit = TRUE) : attempt to use zero-length variable name

Question

Sample data

ACCOUNT <- c("M191212", "M205668", "M197954", "M208966", "M193465", "M207622", "M191869")
PRODUCT <- c(1, 2, 3, 1, 2, 3, 2)
This is made into a dataset by lazy_dt() and as_tibble()   

Code

library(tidyverse)
library(data.table)
library(dtplyr)

data2 <- data %>%
  lazy_dt() %>%
  mutate(YR = substring(ACCOUNT,2,3))%>% #This bit works fine
  mutate(PRODUCT_NAME = dplyr::recode(PRODUCT,
                         `1` = "PROD_A",
                         `2` = "PROD_B",
                         `3` = "PROD_C")) %>%
collect()

When I try to run this I get an error 'Error in env_has(env, var, inherit = TRUE) : attempt to use zero-length variable name'.

I have tracked it down to the recode section. The answers on here relating to the sero-length error suggest it's the back ticks that are the problem, but I have tried changing them to ' i.e. single quote marks, and I still get the same error. PRODUCT is stored as an integer. This code used to run fine a few months ago, but it's now not working. I am using dtplyr 1.2.1.