Recurring Single Post 404 errors

I recently installed Yoast on my networks installation and network activated it. Since then, I’ve been experiencing recurring 404 errors on my single blog post pages on my main site. I thought it was just a permalink thing, and a few times, I just refreshed the permalinks and things went back to normal.

Today, when it happened, without refreshing permalinks, I started deactivating plugins to see if I could relate one to the other. As soon as I deactivated Yoast, my single post started working again without doing anything else.

Has anyone ever experienced this before? I have a hard time believing it is directly related to Yoast, but it’s the only conclusion I can come to. I’m guess it probably has something to do with my htaccess file, so I’ll post that here too:

# Use PHPBETA Single php.ini as default
AddHandler application/x-httpd-phpbetas .php
#WFCACHECODE - Do not remove this line. Disable Web Caching in Wordfence to remove this data.
<IfModule mod_deflate.c>
	AddOutputFilterByType DEFLATE text/css text/x-component application/x-javascript application/javascript text/javascript text/x-js text/html text/richtext image/svg+xml text/plain text/xsd text/xsl text/xml image/x-icon application/json
	<IfModule mod_headers.c>
		Header append Vary User-Agent env=!dont-vary
	</IfModule>
	<IfModule mod_mime.c>
		AddOutputFilter DEFLATE js css htm html xml
	</IfModule>
</IfModule>
<IfModule mod_mime.c>
	AddType text/html .html_gzip
	AddEncoding gzip .html_gzip
	AddType text/xml .xml_gzip
	AddEncoding gzip .xml_gzip
</IfModule>
<IfModule mod_setenvif.c>
	SetEnvIfNoCase Request_URI \.html_gzip$ no-gzip
	SetEnvIfNoCase Request_URI \.xml_gzip$ no-gzip
</IfModule>
<IfModule mod_headers.c>
	Header set Vary "Accept-Encoding, Cookie"
</IfModule>
<IfModule mod_rewrite.c>
	#Prevents garbled chars in cached files if there is no default charset.
	AddDefaultCharset utf-8

	#Cache rules:
	RewriteEngine On
	RewriteBase /
	RewriteCond %{HTTPS} on
	RewriteRule .* - [E=WRDFNC_HTTPS:_https]
	RewriteCond %{HTTP:Accept-Encoding} gzip
	RewriteRule .* - [E=WRDFNC_ENC:_gzip]
	RewriteCond %{REQUEST_METHOD} !=POST
	RewriteCond %{HTTPS} off
	RewriteCond %{QUERY_STRING} ^(?:\d+=\d+)?$
	RewriteCond %{REQUEST_URI} (?:\/|\.html)$ [NC]
	
	RewriteCond %{HTTP_COOKIE} !(comment_author|wp\-postpass|wf_logout|wordpress_logged_in|wptouch_switch_toggle|wpmp_switcher) [NC]
	
	RewriteCond %{REQUEST_URI} \/*([^\/]*)\/*([^\/]*)\/*([^\/]*)\/*([^\/]*)\/*([^\/]*)(.*)$
	RewriteCond "%{DOCUMENT_ROOT}/wp-content/wfcache/%{HTTP_HOST}_%1/%2~%3~%4~%5~%6_wfcache%{ENV:WRDFNC_HTTPS}.html%{ENV:WRDFNC_ENC}" -f
	RewriteRule \/*([^\/]*)\/*([^\/]*)\/*([^\/]*)\/*([^\/]*)\/*([^\/]*)(.*)$ "/wp-content/wfcache/%{HTTP_HOST}_$1/$2~$3~$4~$5~$6_wfcache%{ENV:WRDFNC_HTTPS}.html%{ENV:WRDFNC_ENC}" [L]
</IfModule>
#Do not remove this line. Disable Web caching in Wordfence to remove this data - WFCACHECODE
# Changed PHP handler from application/x-httpd-php54s to application/x-httpd-phpbetas on Fri Dec 18 09:10:10 MST 2015.

# BEGIN WordPress
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]

# add a trailing slash to /wp-admin
RewriteRule ^wp-admin$ wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^(wp-(content|admin|includes).*) $1 [L]
RewriteRule ^(.*\.php)$ $1 [L]
RewriteRule . index.php [L]
# END WordPress

# BEGIN MainWP

# END MainWP

Anybody know what might be going on here?