I encounter this problem when I was trying to show to the customer that it is better to save to an eDrawings Web HTML file (as your smartphone can read an eDrawings file in .html file format).
The Error Writing file messages shows when trying to save as to eDrawings Web HTML file
The issue should be repaired in the latest version of SOLIDWORKS 2022. But in case this error still shows, you can rectify the error by saving the file first (File>Save). After that, you can use the save as command to save the file to eDrawings Web HTML Files (shown below).
*Do note that eDrawings Web HTML files is available to eDrawings Pro 2019 and above
**Measure and move function is now available in eDrawings Web HTML files for eDrawings 2021