Try to change Mode to 11bg mixed. If it is the same, maybe it is defective. Take it back to the shop.

I didn't see such an option on web interface of WA860RE. What you need sounds like client mode supported by some other models like TL-WA90ND.

Power off your computer. Unplug the adapter from PCI slot and find out the model number&hardware version on adapter itself. What's the operating system of your PC? Check the link speed of wireless...

What's the temperature indoor and outdoor? Crashing continues even with UPnP disabled?

According to excerpt of your log, we can see internet connection drops but nothing else. Can you provide the complete log? Besides, provide screenshot of Status---WAN page.

You know V3 is coming out and I'm afraid that there is no newer update for V2 in future... However, since you cannot test and confirm that MA180 is working OK, it is unfair to say that W8968 V2's...