Owncloud : error 502 bad gateway

Hi

I have a recurring problem with ucs and owncloud.

I install owncloud with the ucs image provide on the website.
UCS version is 4.4.4 errata617.
Owncloud version is 10.3.2.2

I use workstation to mount my ucs image.

Sometimes, usually when my computer reboot itself, I have an error 502 when I try to access to /owncloud.

image

I can access to ucs part but not owncloud.

I have this error before and I reinstall everything to have last versions, but no more luck…

Any ideas where the problem came from?

Thank for your help.