Solved my problem, thanks for sharing.
There is a plugin conflict. If you try and edit the membership levels page using TA while the PMPRO block is on the page you will get the error.
If you want to edit the page using TA then first remove the PMPRO block using the Std WP editor. Make your changes with TA. Then go back to the WP editor and add the block back in. This solution make work with the short code as well but I have not tested. If it does it means you will be able to place the levels short code any where on the page. If not the the PMPRO levels table will always be be below the edits you make with TA. Not ideal but workable.
