Theme Editor Issues When Working On Child Theme

I’ve been editing style.css on my child theme for thematic for these few days. Then, I’ve been getting errors when saving the stylesheet last night and today.

WordPress either sends me 10% of the time to a page that says: “Sorry, that file cannot be edited.” or the theme does not exist. It ultimately wiped clean my style.css this afternoon. And I had to restart on css coding again.

In addition, while working on style.css, around 5% of the time when I save the stylesheet, my coding gets quirky.

For instance,

#blog-description
became
#blog-de3cription
after one of my saves.

And previously, the 508px I specified for a div became 5b8px. I really need to know what’s going on.

WordPress either tell me that my file cannot be edited, my file is missing or adds random characters to my coding when I update the file.

I have tried searching on Google and WordPress for the same issue but I either can’t find the issue or there was a similar issue but in a wordpress version outdated by over 5 years.