[ERROR]get node rrddata: Get "https://127.0.0.1:8006/api2/json/nodes/pve04/rrddata?timeframe=hour": context deadline exceeded (Client.Timeout exceeded

it sounds like the request took too long to be processed, your metrics exporter client timed out, and the PVE API server then logged an error caused the client disappeared..
 
I don't know what kind of client you are using there, maybe the timeout is configurable?
 
the timeout is in your client ("exporter")!
 
you tell me :-P it's not something that PVE ships.. look at the log you posted ;)