Yesterday when I tried to use mutate() function to recode some values in a specific column,everything was fine.
But suddenly, I run these codes again today, it returns errors from the line with mutate() function：

Can’t transform a data frame with duplicate names.

Backtrace:

1. EVS_recode %>% mutate_at(c(“C001”), ~na_if(., -1))
2. dplyr::mutate_at(., c(“C001”), ~na_if(., -1))
3. dplyr:::mutate.data.frame(.tbl, !!!funs)
4. dplyr:::mutate_cols(.data, …, caller_env = caller_env())
5. DataMask$new(.data, caller_env)
6. dplyr:::initialize(…)

here are the codes I used which work perfectly yesterday

#recode the 1 in column C001 to be 5, 2 to be 4#

EVS_recode <- EVS_recode %>% mutate(C001= recode(C001, '1' = 5, '2'= 4))

#recode the -1,-2,-4,-5 values to be NA in column C001#

EVS_recode <- EVS_recode %>% mutate_at(c('C001'), ~na_if(.,-1))

EVS_recode <- EVS_recode %>% mutate_at(c('C001'), ~na_if(.,-2))

EVS_recode <- EVS_recode %>% mutate_at(c('C001'), ~na_if(.,-4))

EVS_recode <- EVS_recode %>% mutate_at(c('C001'), ~na_if(.,-5))

This is my first time to have such large scale of codes not working related to mutate()
Could someone help me or has the similar problem when using mutate() ?

Thanks for your time to read this!
It would be very helpful if someone can give me a hint.