Symfony Hub "unavailable"

I have a Symfony Hub connected to my HA on a Pi4. From time to time, it gets “unavailable” and wont receive any commands anymore. At the same time, it still works normally with the Harmony App on my phone.

When i check the log, i have a lot of these in there:

2020-05-18 19:27:50 ERROR (MainThread) [aioharmony.hubconnector] 192.168.178.90: Exception on post: Connection timeout to host http://192.168.178.90:8088/
2020-05-18 19:27:50 ERROR (MainThread) [aioharmony.hubconnector] 192.168.178.90: Unable to retrieve HUB id
2020-05-18 19:27:50 WARNING (MainThread) [homeassistant.components.harmony.remote] Harmony: Unable to connect to HUB.
2020-05-18 19:27:50 WARNING (MainThread) [homeassistant.config_entries] Config entry for harmony not ready yet. Retrying in 5 seconds.

anyone has any idea?