Example of robustly subscribing to BLE gatt characteristicvaluechanged

While I'm working on this, I've realised that the Bangle.js 1 I have often doesn't find the BLE device, yet my phone or laptop does find it.

  NRF.requestDevice({ timeout:4000,
                      active:true,
                      filters: [{ namePrefix: 'XXX_' }] 

I added 'active' and a long 'timeout' to try have the best luck; but still very often (more times than not) I get:

Error: No device found matching filters

while my Android phone, or a JS app in Chrome on my laptop, discovers the device just fine.

I see the nRF chip in Bangle 2 is different; might I have better luck with a Bangle 2?