Tvheadend

I've built the latest git using:
./configure --disable-avahi --enable-bundle --disable-zlib --release
and I'm running it on a QNAP x86 NAS.

Randomly some elements of the UI are not displayed and loaded correctly and there are errors in the TVHeadend debug log.
Sometimes they are a lot, other times only a few (I think that's because the Firefox browser saves the items in the cache).

Example 1
Dec 01 15:51:33 [ERROR]:webui: failed to open src/webui/static/extjs/resources/images/default/grid/col-move-bottom.gif
Dec 01 15:51:33 [ERROR]:HTTP: 192.168.1.1: /static/extjs/resources/images/default/grid/col-move-bottom.gif -- 500
Dec 01 15:51:33 [ERROR]:webui: failed to open src/webui/static/extjs/resources/images/default/grid/loading.gif
Dec 01 15:51:33 [ERROR]:HTTP: 192.168.1.1: /static/extjs/resources/images/default/grid/loading.gif -- 500
Dec 01 15:56:03 [ERROR]:webui: failed to open src/webui/static/extjs/resources/images/default/sizer/nw-handle.gif
Dec 01 15:56:03 [ERROR]:HTTP: 192.168.1.1: /static/extjs/resources/images/default/sizer/nw-handle.gif -- 500
Dec 01 15:56:03 [ERROR]:webui: failed to open src/webui/static/extjs/resources/images/default/sizer/se-handle.gif
Dec 01 15:56:03 [ERROR]:HTTP: 192.168.1.1: /static/extjs/resources/images/default/sizer/se-handle.gif -- 500

Example 2
Dec 01 16:04:12 [ERROR]:webui: failed to open src/webui/static/extjs/resources/images/default/panel/left-right.gif
Dec 01 16:04:12 [ERROR]:webui: failed to open src/webui/static/extjs/resources/images/default/panel/top-bottom.gif
Dec 01 16:04:12 [ERROR]:HTTP: 192.168.0.7: /static/extjs/resources/images/default/panel/left-right.gif -- 500
Dec 01 16:04:12 [ERROR]:HTTP: 192.168.0.7: /static/extjs/resources/images/default/panel/top-bottom.gif -- 500

Example 3
Dec 01 16:07:25 [ERROR]:webui: failed to open src/webui/static/icons/world.png
Dec 01 16:07:25 [ERROR]:HTTP: 192.168.0.7: /static/icons/world.png -- 500
Dec 01 16:07:25 [ERROR]:webui: failed to open src/webui/static/multiselect/resources/bottom2.gif
Dec 01 16:07:25 [ERROR]:HTTP: 192.168.0.7: /static/multiselect/resources/bottom2.gif -- 500

Example 4
Dec 01 16:07:57 [ERROR]:webui: failed to open src/webui/static/livegrid/resources/css/ext-ux-livegrid.css
Dec 01 16:07:57 [ERROR]:HTTP: 192.168.0.7: /static/livegrid/resources/css/ext-ux-livegrid.css -- 500
Dec 01 16:07:57 [ERROR]:webui: failed to open src/webui/static/extjs/ext-all-debug.js
Dec 01 16:07:57 [ERROR]:HTTP: 192.168.0.7: /static/extjs/ext-all-debug.js -- 500
Dec 01 16:07:58 [ERROR]:webui: failed to open src/webui/static/extjs/resources/images/default/form/trigger.gif
Dec 01 16:07:58 [ERROR]:webui: failed to open src/webui/static/extjs/resources/images/default/grid/grid-blue-split.gif
Dec 01 16:07:58 [ERROR]:HTTP: 192.168.0.7: /static/extjs/resources/images/default/grid/grid-blue-split.gif -- 500
Dec 01 16:07:58 [ERROR]:HTTP: 192.168.0.7: /static/extjs/resources/images/default/form/trigger.gif -- 500
Dec 01 16:07:58 [ERROR]:webui: failed to open src/webui/static/extjs/resources/images/default/grid/refresh-disabled.gif
Dec 01 16:07:58 [ERROR]:HTTP: 192.168.0.7: /static/extjs/resources/images/default/grid/refresh-disabled.gif -- 500
Dec 01 16:07:58 [ERROR]:webui: failed to open src/webui/static/icons/eye.png
Dec 01 16:07:58 [ERROR]:HTTP: 192.168.1.1: /static/icons/eye.png -- 500
Dec 01 16:07:58 [ERROR]:webui: failed to open src/webui/static/icons/information.png
Dec 01 16:07:58 [ERROR]:webui: failed to open src/webui/static/icons/wrench.png
Dec 01 16:07:58 [ERROR]:HTTP: 192.168.0.7: /static/icons/wrench.png -- 500
Dec 01 16:07:58 [ERROR]:HTTP: 192.168.0.7: /static/icons/information.png -- 500

I've checked the build.linux/bundle.c and the files are there.
The same happens when building with the --enable-zlib option.