Error in gsub: input string 4 is invalid in this locale

Hi!
I'm pretty new to shiny and shinyapps and I ran into a problem while deploying my app. I have two plot_ly plots in the code that show up without any problem on my local instance but I keep getting an error on the shiny app. This is what's written in the logs about it: "Warning: Error in gsub: input string 4 is invalid in this locale". Does anyone know how to solve this issue?

Thanks!