all fixings and settlements that are set by consensus of a limited few are dubious. libor, fx, platts, ...
The day of fading violent moves 60 secs before the fix are long gone, but the london fix, cut and frankfurt open/london open are probably the remaining key times that everyone knows about where you'll see manipulation/extreme delta hedging/clearing of orders but now over a longer timeframe. How you describe it is immaterial, I genuinely think a lot of it is just part of the market mechanics rather than dark forces. The more subtle stuff is price and time manipulation which happens daily. You can call them liquidity tests, inefficiencies, broker shading whatever but it's an intrinsic part of the market in FX for sure. And probably every other market too.
Framing the question a different way will provide the answers you seek. What is Liquidity? Who offers it? Who takes it? Who wants to do business? Who has to do business? When is the above efficient and balanced? When is the above inefficient and imbalanced? Use different keywords to open different mental locks.