I just loaded the newest version of R studio with R for mac:

version
               _                           
platform       aarch64-apple-darwin20      
arch           aarch64                     
os             darwin20                    
system         aarch64, darwin20           
status                                     
major          4                           
minor          5.2                         
year           2025                        
month          10                          
day            31                          
svn rev        88974                       
language       R                           
version.string R version 4.5.2 (2025-10-31)
nickname       [Not] Part in a Rumble     

I noticed that it now seems to accept ambiguous references to columns. This is bad! Here is an example.

df <- data.frame(people = c('Susan', 'Mike', 'Gary', 'Wayne'), Age2 = c(2,24,35,1))

df$Age2 df$Age # this should be NULL but gives df$Age2

"Age2" %in% colnames(df) # it correctly tells us that 'Age2' is among the column names "Age" %in% colnames(df) # it correctly tells us that 'Age' is not among the column names.

You might want to check the version you are running with the code above.

I've not encountered a problem like this before. I will contact R Core Team.