Listing all services returns 502 or 504

[pierrePro]

I had no issues wednesday when I quit work. This monday I have 50x errors when I try to access the list of my services through the api. When I try to access the frontend interface, I have 504 or 502 errors.
Nothing was done between friday and this morning.
If I try to access just one service through the api or through the navigator (dashboard/edit_service/#), it works.
If I try to access dashboard/services, no services are listed.
When I look at the logs, there are no errors and the websites are still pinged as the logfile increments itself.
I use version 0.91.0 on a debian.
Any ideas would be welcome.