Nginx cache 1 KEY into multiple cache files (cache not running)

[semseoymas]

Some more interesting data: sometimes it HIT cache, sometimes not.....
depending of referer???? I do not know how... I cannot imagine why.

(consecutive log lines filtering by uri.... I did not remove any file or
cache, even not restarted nginx at all)

107.167.108.187 - - [19/Nov/2015:05:22:22 +0100] "GET
/wp-content/themes/sahifa/timthumb.php?src=/wp-content/uploads/2014/06/Clotilde.jpg&h=50&w=50&a=c
HTTP/1.1" 200 2082
"http://xxxxxx.com/2014/09/significado-del-nombre-daniela/" "Opera/9.80
(X11; Linux zvav; U; es) Presto/2.12.423 Version/12.16" Exec: "0.020" Conn:
"6" Mobile: "-" Cache: MISS (0.020 sec) - Upstream: "200"
107.167.108.187 - - [19/Nov/2015:05:22:23 +0100] "GET
/wp-content/themes/sahifa/timthumb.php?src=/wp-content/uploads/2014/06/Clotilde.jpg&h=50&w=50&a=c
HTTP/1.1" 200 2082
"http://xxxxxx.com/2014/09/significado-del-nombre-daniela/" "Opera/9.80
(X11; Linux zvav; U; es) Presto/2.12.423 Version/12.16" Exec: "0.000" Conn:
"4" Mobile: "-" Cache: HIT (- sec) - Upstream: "-"
107.167.108.195 - - [19/Nov/2015:05:23:11 +0100] "GET
/wp-content/themes/sahifa/timthumb.php?src=/wp-content/uploads/2014/06/Clotilde.jpg&h=50&w=50&a=c
HTTP/1.1" 200 2082
"http://xxxxxx.com/2014/09/significado-del-nombre-daniela/" "Opera/9.80
(X11; Linux zvav; U; es) Presto/2.12.423 Version/12.16" Exec: "0.037" Conn:
"8" Mobile: "-" Cache: HIT (- sec) - Upstream: "-"
37.132.144.110 - - [19/Nov/2015:05:24:28 +0100] "GET
/wp-content/themes/sahifa/timthumb.php?src=/wp-content/uploads/2014/06/Clotilde.jpg&h=50&w=50&a=c
HTTP/1.1" 200 2082 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:42.0)
Gecko/20100101 Firefox/42.0" Exec: "0.024" Conn: "1" Mobile: "-" Cache: MISS
(0.023 sec) - Upstream: "200"
37.132.144.110 - - [19/Nov/2015:05:24:31 +0100] "GET
/wp-content/themes/sahifa/timthumb.php?src=/wp-content/uploads/2014/06/Clotilde.jpg&h=50&w=50&a=c
HTTP/1.1" 304 0 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:42.0)
Gecko/20100101 Firefox/42.0" Exec: "0.000" Conn: "2" Mobile: "-" Cache: HIT
(- sec) - Upstream: "-"
107.167.108.195 - - [19/Nov/2015:05:24:45 +0100] "GET
/wp-content/themes/sahifa/timthumb.php?src=/wp-content/uploads/2014/06/Clotilde.jpg&h=50&w=50&a=c
HTTP/1.1" 200 2082
"http://xxxxxx.com/2014/09/significado-del-nombre-daniela/" "Opera/9.80
(Android; Opera Mini/11.0.1912/37.7126; U; es) Presto/2.12.423
Version/12.16" Exec: "0.038" Conn: "6" Mobile: "-" Cache: MISS (0.038 sec) -
Upstream: "200"

and the files:

root at hyperserver [/var/nginx.cache/xxxx]# find -type f -exec grep -a "KEY:
/wp-content/themes/sahifa/timthumb.php?src=/wp-content/uploads/2014/06/Clotilde.jpg&h=50&w=50&a=c"
{} \;
KEY:
/wp-content/themes/sahifa/timthumb.php?src=/wp-content/uploads/2014/06/Clotilde.jpg&h=50&w=50&a=c
KEY:
/wp-content/themes/sahifa/timthumb.php?src=/wp-content/uploads/2014/06/Clotilde.jpg&h=50&w=50&a=c
KEY:
/wp-content/themes/sahifa/timthumb.php?src=/wp-content/uploads/2014/06/Clotilde.jpg&h=50&w=50&a=c
root at hyperserver [/var/nginx.cache/xxxx]# find -type f -exec grep -la "KEY:
/wp-content/themes/sahifa/timthumb.php?src=/wp-content/uploads/2014/06/Clotilde.jpg&h=50&w=50&a=c"
{} \;
./7/d2/39815042547bf336bfe0c8de84e17d27
./6/73/c1463df2aaa737d2616ba5016c64f736
./2/9c/edda94a8edf68a32eb83011e918a59c2

As you see, multiple files for the same KEY (request_uri)... sometimes MISS,
sometimes HIT... I cannot imagine why.

Please, could someone help me or give a clue?

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,262943,262945#msg-262945