WiFi doesn't work at certain angles, only on flat surfaces!

I have a bizarre problem with my MacBook Air. The WiFi only works only on stable, hard and flat surfaces. The WiFi is unusable in any other kind of situation: lying in bed, sitting on the sofa, using it on your lap etc...

It doesn't lose connection to the router, it just doesn't connect to the internet regardless of the router type and speed (I have tested it on 5 separate routers, in 5 separate locations).

What might have contributed to the problem, was that the MacBook had an extremely small amount of liquid damage impairing the keyboard usage (a few sticking keys) and was given to Apple for repair. Whilst being repaired, Apple damaged it further, admitted liability and fixed the relevant parts. However since that point, the WiFi only works only on stable, hard and flat surfaces and at any other angle, it drops internet connection.

Apple refuse to admit liability for this problem now (even though it only started AFTER they took it back in for second repair, admitting their fault in further damage) and instead state that it "could" be the liquid damage, no matter how small.

While I agree of course it could be the liquid damage, it seems a really unusual and specific problem for that to be totally the issue.

Has anyone ever had a similar experience or have any ideas of how I may find out a way to work out exactly what the problem is!?

Thank you for any help.