The only seal in the blue circle is supposed to be between the traps flat washer and the waste fitting. I know you said the washer is in there but is it tight enough? the telescopic part moves independently of the bottle so no need to worry about getting it in the correct orientation while tightening it. You could try another washer, that waste and trap should mate perfectly together unless there is a manufacturing issue. Make sure the black back nut it sealed properly to the china to rule that out, it could be running down the thread, as someone else said put some plumbers mait in or silicone. Using any PTFE or loctite on the thread is a bodge.
Try one of these for the pipe in the wall -
Upgrade your plumbing connections with the Straight Cp Brass x ABS Connector, ensuring durability and efficient water flow.
mcalpineplumbing.com
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or maybe -
Achieve versatile connections with the Straight Connector, featuring Pushfit x Solvent Weld for flexibility in your plumbing system.
mcalpineplumbing.com
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Mcalpine do 1m lengths of chrome pipe, so if you wanted it going outside you could use this where it exits -
90° ABS solvent weld Bend x 32mm European pipe size Ring Seal Pushfit
mcalpineplumbing.com
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Not sure what trap you got but you could get a Mcalpine trap, at least then you know all the above is definitely compatible, although what you have is probably 32mm