How to fix Error in FUN(left, right) : non-numeric argument to binary operator

Question

When i run the code below in R, I get the error: 'FUN(left, right) : non-numeric argument to binary operator'. I tried to fix this by converting the variables that are characterized as 'character' to numeric variables by using the code : as.numeric(). However, NA's are introduced by coercion when I try to use that operator. As a result, the whole column in my datafram is empty as it shows only NA's for every row. Does anyone know to to fix this error? Thank you in advance!

library(tidyverse)
library(readr)
sessie_03 <- read_csv("~/Downloads/sessie_03.csv")
View(sessie_03)
sessie_03 <- read.csv("~/Downloads/sessie_03.csv", header =  TRUE, sep = ",")
stars_master <- read.csv("~/Downloads/stars_master.csv", header = TRUE, sep =";")
stars_numbers <- read.csv("~/Downloads/stars_numbers.csv", header = TRUE, sep = ";", dec = ",")

new_stars_master <- tibble(Title.id = sessie_03$title_id,
                          Title.year = sessie_03$Year,
                          Star1.name = sessie_03$imdb.com_star1_name,
                          Star1.id = sessie_03$imdb.com_star1_id,
                          Star2.name = sessie_03$imdb.com_star2_name,
                          Star2.id = sessie_03$imdb.com_star2_id,
                          Star3.name = sessie_03$imdb.com_star3_name,
                          Star3.id = sessie_03$imdb.com_star3_id,
                          )

new_stars_numbers <- tibble(Star.id = stars_numbers$imdb_com_star_id,
                            Title.year = stars_numbers$ï..year,
                            "Title.year+1" = stars_numbers$ï..year + 1,
                            Star.rank = stars_numbers$the_numbers_com_starpower_rank
                            )


STP <- tibble(Title.id = new_stars_master$Title.id,
              Star1.id = new_stars_master$Star1.id,
              Star1.name = new_stars_master$Star1.name,
              Star1.rank = new_stars_master %>% left_join(new_stars_numbers, by = c("Star1.id" = "Star.id",
                                                                                    "Title.year" = "Title.year+1"))
                                            %>% select(Star.rank),
              Star2.id = new_stars_master$Star2.id,
              Star2.name = new_stars_master$Star2.name,
              Star2.rank = new_stars_master %>% left_join(new_stars_numbers, by = c("Star2.id" = "Star.id",
                                                                                    "Title.year" = "Title.year+1"))
                                            %>% select(Star.rank),
              Star3.id = new_stars_master$Star3.id,
              Star3.name = new_stars_master$Star3.name,
              Star3.rank = new_stars_master %>% left_join(new_stars_numbers, by = c("Star3.id" = "Star.id",
                                                                                    "Title.year" = "Title.year+1"))
              %>% select(Star.rank),
              Star.power = (Star1.rank + Star2.rank + Star3.rank ) /3
)