Raspberry Pi pico can not download other programs

I have a question, I copied the program into Raspberry Pi pico when I was working on the project of thermal printer parking system, after that I tried to copy other programs but they failed, is it because the pico board can only copy one program?

You can copy multiple files to the root directory depending on their size. But only one file can be executed at once otherwise the currently executing python file depend on the existing files. What is the error output you get when copying? Please provide the error output.