Parse error in three files every few days after upgrading to 2.8

I upgraded 4 of my WP sites and one is giving me issues.

It is https://bikramhotyoga.ca

Every few days it bugs out and I get a parse error in the index.php. I replace that file and it then gives me parse errors with default-filters.php and default-widgets.php in the wp-includes folder.

After I replace those two files all works, but in a couple days I get the errors again. Same ones everytime.

Any suggestions on what is going on and why this is happening?

Mike