Hey guys! Recently bought a dc2 and it seems the car has an intermittent sticky throttle body cable problem. Used the search function but could only find high-low idle problems or problems with the TB sticking when accelerating

Bit of a background:
During one of the inspections prior to purchasing the car, the car was sitting on high idle (around 3k rpms) and as a result I didnt go ahead with the sale on that particular occasion. However, the seller got his mechanic to come around and "fixed" the issue as he said all that needed to be done was to tighten the nut connected to cable. Thought all was well as the high idle had gone away and bought the car.

But in the 1 month period since I bought the car, the problem has come up two more times and both times have been where the car has been driven to around 5-6k rpms (Note: Haven't vtec'd the car much at all cause I still need to convert my P plates to manual).

I can easily resolve the issue by tugging the cable down and restoring normal idle but does anyone know what the underlying problem is? Essentially can't drive the car hard at all if I want to avoid the problem :S
I've attached some photos to explain what I mean.

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What the cable should look like. should return to this position after accelerating.

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Position the cable was stuck at, causing the butterfly valve to be stuck open and the 3k rpm idle.