While might not be exactly answer to your problem; I faced lots of connectivity issues with Volumio, but not with integration startup, but perhaps something worth to check…
So, are you using Volumio over WiFi? I found it to be very unstable… even connecting via web browser or from native application very frequently I faced issues with reconnecting (finding in case of app) the volumio instance (on RPi 3B+). Also HA was frequently loosing connection, generating lots of entries in log. All of this gone after I switched to ethernet connection. Interesting it is still over WiFi, as now Volumio is connected to WiFi mesh note, that commnicates with mesh root over radio… So this also somehow indicate, that the problem was not really with WiFi itself, but elsewhere - I tried to find some solution to this and all I found was that there is some problem with WiFi driver in underlying OS in Volumio itself.
Maybe the problem is solved. Noticed that Home assistant thinks that Volumio is Openhome due to the UPNP discovery. Noticed connection errors in the logs and also the entity mentioned Openhome as integration.
Disabled UPNP on Volumio via Settings -> Sources -> UPNP Renderer