Can't connect to MDBT42Q module reliably

Hi there!

I bought 10 pre-flashed MDBT42Q modules to solder onto my own boards that I designed. I've hand-soldered two of them, but can't connect to them reliably over BLE. I can only see the first board's module every now and again when I scan for it from the Espruino Web IDE, and it fails to connect to it. I'm suspecting it could be an issue with the soldering - is there a guide somewhere on how to properly hand-solder these modules?

With the second board I can at least see it every time I scan for it (which is why I'm suspecting bad soldering with the first board), but it's still not connecting reliably. Here is the output from the console log:

>>> Connecting...
Set Slow Write = true
BT> Pre-paired Web Bluetooth device already found
>>> Connecting to MDBT42Q 5ebb
BT>  Device Name:       MDBT42Q 5ebb
BT>  Device ID:         uqDPqM8TCHh0fht7a3w0tg==
>>> Connected to BLE
BT> Connected
>>> Configuring BLE...
BT> Got service
>>> Configuring BLE....
BT> RX characteristic:{}
>>> Configuring BLE....
>>> Configuring BLE.....
BT> TX characteristic:{}
>>> Configuring BLE.....
Set Slow Write = false
>>> BLE configured. Receiving data...
Connected {portName: "MDBT42Q 5ebb"}
Got ""
No Prompt found, got undefined - issuing Ctrl-C to try and break out
Splitting for Ctrl-C, delay 250
Still no prompt - issuing another Ctrl-C
Splitting for Ctrl-C, delay 250
>>> Sending...
---> "\u0010print(\"<\",\"<<\",JSON.stringify(process.env),\">>\",\">\")\n"
>>> Sent
>>> Receiving...
No result found for "process.env" - just got ""
>>> 
[notify_error] Unable to retrieve board information.
Connection Error?
Device found {"portName":"MDBT42Q 5ebb"}
[success] Connected to MDBT42Q 5ebb (No response from board)
>>> Connected to MDBT42Q 5ebb (No response from board)

Any ideas on how can I debug this further?