An enabled downlink plus an MQTT proxy is enough to drown a mesh node. The BLE queue overflows and transmission stalls. The right setting is two switches.
A silent node that no longer transmits is not always a hardware fault. It is often a logical saturation of the link, created by the configuration itself.
The regional firehose
When downlink is enabled and an MQTT proxy relays traffic, the node receives the entire regional mesh. Every remote message flows back down the BLE link to the terminal.
The BLE transmit queue is small. It fills faster than it drains. Local packets waiting to be sent stay stuck behind the inbound flow. The node looks mute while it is actually drowning.
The correct setting
Downlink off, uplink on. The node pushes its own frames to the network but is not flooded by the proxy return path. The BLE queue breathes again and transmission resumes.
Mesh routing works by managed flood, not by routing table. Each node rebroadcasts once, with a hop counter. There is no route to look for: the real lever is inbound volume, not topology.