I encounter this bug when updating plugins:
500 Internal server error Internal server error The server has detected an internal error or an incorrect configuration and could not complete your request. Contact the server administrator at firstname.lastname@example.org to notify him of the time of the error and the actions you took immediately before this error. You may find more information about this error in the server error log.
That was a week ago, so I do not think it's the problem of the busy server. I opened the log and found nothing new. I put
WP_DEBUG too true and that's what I got:
Warning: An unexpected error has occurred. There may be a problem with WordPress.org or the configuration of this server. If you continue to have problems, try the support forums. (WordPress was unable to establish a secure connection to WordPress.org. Contact your server administrator.) In /home/lightnin/domains/xn--qucu-hr5aza.cc/public_html/wp-includes/update.php on line 384
Since I did not touch anything in wp-includes, I do not know why that happens. After I received this message, the plugins were updated.
So this problem is solved, but I wonder if anyone can provide more insight into this.