Production at the Schiehallion oil field west of Shetland has stopped once again to allow essential maintenance to be carried out.
Scheduled work on the floating storage and production vessel had already halted output during the summer months.
Oil started flowing from it in recent weeks, but now a new bout of gremlins need to be sorted out.
The latest shutdown will mean more lost income to the council, which gains money from handling tanker traffic through its port.
Speaking at this week’s harbour board meeting, chairman Alastair Cooper said Schiehallion traffic accounted for 40 per cent of revenue going through Sullom Voe when it was working properly.
Last year the council lost £1 million in income following an extended five month shutdown, brought about when the Lerwick-registered shuttle tanker Loch Rannoch nudged Schiehallion, damaging a hose reel.
At this week’s harbour board meeting, neither Mr Cooper or head of ports and harbour Roger Moore could explain the latest set-back.
Captain Moore told committee members: “At the present moment in time production has stopped. I have enquired as to why or for how long, but other than that, all I can say is that there is no production at the moment.”
A spokeswoman for BP said Schiehallion was shut down for “essential maintenance”. She would not be drawn on any details about the work, maintaining it was “part of normal ongoing operational management of the facility”.
“We acknowledge there have been some challenges with Schiehallion, but would stress that it is a great asset for us with a great future.
“We are therefore working with the Schiehallion partnership to assess options for maximising the life of the field going forward.”
There has been speculation recently within the oil industry that BP is about to spend £1.3 billion building a new floating production ship which could replace Schiehallion in five years time.
Meanwhile the Loch Rannoch is due to undergo scheduled maintenance following her stint in the Gulf of Mexico.
She was used to help in the clear up operation after the Deepwater Horizon drilling rig exploded in April, killing 11 workers and creating the environmental disaster that sparked demands for deep water drilling to be brought to an end.
In Shetland Greenpeace protesters recently attached themselves to the Chevron-operated deep-water drilling vessel Stena Carron off Bressay. They continued their campaign by swimming in front of her out at sea, blocking her progress.
Isles MP Alistair Carmichael, meanwhile, has welcomed news there will be no blanket moratorium on deep sea drilling among EU states.
The European Parliament has already rejected calls for a moratorium.
However there were reports the EU energy commissioner would propose a total ban on deep water oil exploration.
Instead he announced national governments will retain control over the approval process for new installations – a move Mr Carmichael has described as “a welcome blast of commonsense” – particularly since the Obama administration has lifted such a ban in the US.
“In the week that the US government lifted their ban on new deep sea drilling in the Gulf of Mexico, an EU moratorium would have been bad news for Scotland.
“Of course we need to take steps to protect the natural environment around rigs – as well as the people working offshore – but a blanket ban would have been excessive and put thousands of jobs at risk.
“This decision from the energy commissioner is a welcome blast of commonsense, and will allow us to look again at the rules to see where improvements can be made without threatening the future of a sector that is vital to our local economy.”