QNAM having trouble reaching server

This is a strange issue to describe so bear with me.

I'm running a GUI QML program that uses a QML Map QuickItem with a private map server. The map server is running as a virtual machine on another computer and has its own IP (through a bridged adapter).

When the GUI pc has no wifi connection (both map server and gui pc are on the same wired network, and the IP used to access the map is the wired one, doesn't even have wireless IP), the map is always blank. I can ping the map server pc, and I can even download the png images from it, but the QML Map shows nothing. 

If I turn on the WiFi, the map suddenly comes to life, I get the message

QNetworkReplyHttpImplPrivate::_q_startOperation was called more than once Qurl("http://10.10.1.25/basemap/6/34/22.png")

and it all works fine, even if then I turn off the wifi, tiles still keep getting downloaded.

What is preventing the tiles from being accessed when starting the GUI with ethernet only?

Sorry, can't really get you a working example, but here's my plugin code:

PluginParameter {name: "osm.mapping.custom.host"; value: "http://10.10.1.25/basemap/"}
PluginParameter {name: "osm.mapping.cache.directory"; value: "/tmp/" }