How to Fix “Source file could not be read” Error on Firefox?

While attempting to download a file from the internet, Firefox may show a “File could not be saved because the source file could not be read” error message. In ‘File,’ the file’s path will be mentioned – like appdatalocaltemp, for instance. It can also ask you to attempt again later or contact the server administrator. If you encounter this problem even in Firefox Quantum, here is what you require to do to solve the issue. Here are some steps mentioned below.