The issue seems to be resolved after a restart of all the services linked to Git server.

We requested a restart for all the services that are used for the Git server.

We are still investigating why the server is slow to respond. However, we can confirm the issue is not the maintenance done earlier, and the status degraded by itself to downtime with most of the requests getting timed out.

Our Git server is unstable, it seems response delay is much higher than usual.
We are investigating if the instability is due to the backup system being forced.