Why, after the cache settings in the .htaccess stopped working ajax requests to php files?

Good day!
A colleague decided to try to configure caching and pasted the code in .htaccess which is derived in the end of the question. After that all Ajax requests that go to files .php return 500 error. The feeling was zacchiroli empty files .php which is request. Only helps to resave the file, then the error disappears, but only for a while. Code .htaccess removed, but errors still arise from time to time. Who faced with similar? Is there a way to fix it?
Thanks in advance.
<ifmodule mod_expires.c>
 # Add correct content-type for fonts
 AddType application/vnd.ms-fontobject .eot
 AddType application/x-font-ttf .ttf
 AddType application/x-font-opentype .otf
 AddType application/x-font-woff .woff
 AddType image/svg+xml .svg

 # Compress compressible fonts
 AddOutputFilterByType DEFLATE application/x-font-ttf application/x-font-opentype image/svg+xml

 ExpiresActive On
 ExpiresDefault "access plus 5 seconds"

 # special MIME type for icons - see http://www.iana.org/assignments/media-types/image/vnd.microsoft.icon
 AddType image/vnd.microsoft.icon .ico
 # now we have icon MIME type, we can use it
 # my favicon doesn't change much
 ExpiresByType image/vnd.microsoft.icon "access plus 3 months"

 # Cache Images
 ExpiresByType image/x-icon "access plus 2592000 seconds"
 ExpiresByType image/jpeg "access plus 2592000 seconds"
 ExpiresByType image/png "access plus 2592000 seconds"
 ExpiresByType image/gif "access plus 2592000 seconds"
 ExpiresByType image/svg+xml "access plus 2592000 seconds"

 # Cache Fonts
 ExpiresByType application/vnd.ms-fontobject "access plus 2592000 seconds"
 ExpiresByType application/x-font-ttf "access plus 2592000 seconds"
 ExpiresByType application/x-font-opentype "access plus 2592000 seconds"
 ExpiresByType application/x-font-woff "access plus 2592000 seconds"
 ExpiresByType image/svg+xml "access plus 2592000 seconds"

 # Cache other content types (Flash, CSS, JS, HTML, XML)
 ExpiresByType application/x-shockwave-flash "access plus 2592000 seconds"
 ExpiresByType text/css "access plus 604800 seconds"
 ExpiresByType text/javascript "access plus 2592000 seconds"
 ExpiresByType application/javascript "access plus 2592000 seconds"
 ExpiresByType application/x-javascript "access plus 2592000 seconds"
 ExpiresByType text/html "access plus 600 seconds"
 ExpiresByType application/xhtml+xml "access plus 600 seconds"
</ifmodule>
June 14th 19 at 18:21
0 answer

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