Less Parse Issue

I'm upgrading from version 4.0.3 to 4.1.1 - all seemed to go fine but now the site is unusable as I'm getting a less parse error (along with the google logo):

[font=arial, sans-serif][size=4]LESS parse error: failed at `[/size][/font]

.helper-container .search-input {

.gradient (#f7f7f7, #fdfdfd);


400. That’s an error.

The requested URL was not found on this server

Deleting the code just causes another parse issue.

I've tried clearing the cache and cloning the theme but nothing is working. Any ideas? very frustrating.

Update: this only happens when the my_changes addon is enabled - even if I have no changes in my directory at all.