Yun server blocks with mobile browser - /usr/sbin/uhttpd at 85%

The Yun is configured with php 5.4.5, ans I have made a php page for displaying infos of the 32U4 part, and datas stored in a file.
When I see the php page (also http://192.168.1.162/sd/ecs.php ) on a Windows PC, all Chrome, IE and Firefox browser, the page is always served correctly.

If I take my mobile Samsung Note3 with Android 5, the Yun blocs, randomly (native browser or Chrome), or answer "The CGI process did not produce any reponse"

In order to find the source of the problem, I have made a simplified php page, without the 32U4 infos, letting only the "pure" Linux machine working: same result.

I launch PuTTY, seeing the top monitoring: I discover the process uhttpd constantly high at 81-84% for a while:

Mem: 42072K used, 19044K free, 0K shrd, 5276K buff, 18740K cached
CPU:  41% usr  58% sys   0% nic   0% idle   0% io   0% irq   0% sirq
Load average: 1.60 1.43 1.01 3/59 23271
  PID  PPID USER     STAT   VSZ %VSZ %CPU COMMAND
 1472     1 root     R     1584   3%  81% /usr/sbin/uhttpd -f -h /www -r ecs1 -
  816   573 root     S     5844  10%  15% python -u bridge.py
20318     2 root     SW       0   0%   1% [kworker/0:0]
 1543     1 root     S N   1496   2%   0% {uSDaemon} /bin/sh /sbin/uSDaemon

Python bridge process stays at 15-16%.

The only difference I noticed is the answer port (php: _SERVER["REMOTE_PORT"] ) of the browser: with Windows browser around 50000 - 65400; On Android around 37500.

Any idea?