I have no idea what's going on here. Checked for other references on m_callbackSent but can't see anything which would require the increment to happen before the callback.
I originally thought calling pScan->stop(); explicitly was causing issues (like #242), as it appeared as though letting NimBLEClient::connect() implicitly stop the scan would avoid the issue, but it seems to not be true anymore.

It makes sense now.
Incrementing after meant that there was a risk of a dangling pointer since the scan could be stopped within the onResult callback. Best to always have the callback "last" when possible.

Yes, I'm not sure why it was changed but that would be the reason for the crashing.