WP is notorious for this. The 504 errors are due to how bloated and inefficient it is...it's timing out while trying to finish processing. Our system doesn't log which file is causing the load so we can't tell what is causing it, with Wordpress installations on your account, I'm not at all surprised you keep getting load suspensions.
Please be more mindful of your load and consider dumping Wordpress.
Since you've been suspended twice for this now, we expect this to be fixed promptly. A third suspension for load may be permanent if you haven't made an effort to fix it.