I have a weird problem with internet connection. I connect to wifi with my PC and all seems right until something invisible happens (while idle or while doing something, it seems random) and everything becomes unreachable. Computers in the same network or local hosts, all become immediately unreachable (I have observed this while controlling an online action game through synergy). No applet reports any problems. When this happens, trying to ping something results in a long waiting time and a reply that destination host unavailable.
I tried to make it forget the network and set it up again, but to no avail. I tried to replace network-manager with wicd, but it happened again (this leaves me worried that even reinstalling Ubuntu might not fix it). It does not appear to happen on Windows, but I might have been simply using it too little (and I do not wish to switch to Windows).
Disconnecting and connecting again fixes the problem temporarily, but it is very annoying because I am controlling the PC via synergy.
I have searched some logs and it seems to appear together with a message about switching bandwidth. I am not certain if it really correlates with the error or if it is relevant.
According to lspci, the card is Qualcomm Atheros QCA6174 802.11ac Wireless Network Adapter (rev 32). I am using Ubuntu 16.04 64-bit.