Workers in the TBM, a machine named Grace, reported a potential mechanical issue approximately 4 km along the alignment.
Since then damage to the screw conveyor, which moves excavated material away from the front of the TBM, has been identified.
As a precautionary measure the other TBM, known as Sandy, was also stopped and inspected, confirming hairline cracks in the same part of the machine.
Two new screw conveyors are currently being manufactured and will be fitted once Grace and Sandy have arrived at Redcliffe Station later this year.
It is estimated repair works will be completed in late February, after which the TBMs will continue their journey.
Despite the delays to tunnelling, works are continuing across nine construction sites, while segment production has reached 91 per cent completion.
Later this month the now redundant main drain pipes, replaced by new pipes laid by a microtunnelling machine last year, will be removed.
For more information visit the Forrestfield-Airport Link website.
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