su_post error 503

Hello Vladimir and all the people,
Yesterday I checked that 2 post didn’t work.
My Apache error log gave me this fatal error: allowed memory.
I upgrade this value in php.ini to 256MB but Apache show me the same error.
I update again to 512MB and the Apache gave me other error about the FastCGI protocol.
I checked the plugins in use in this 2 post and only one are common: shortcodes.
I disabled shortcodes and the posts was working again.
I compare the wp_content of both, and I check that the post A was calling to post B with shortcode (su_post), and the post B was calling to the post A with shortcode (su_post).
I re-enabled the plugin, the posts didn’t work again. After I only removed in the post A the sortcode and in the post B I kept the same content, and now the 2 post are working.

I only want tell you my experience for if can you check this matter and you re-code this code if it is necessary.

Thanks!
Best Regards!