The new bridge over the Forth suffered a further months-long setback before work was halted by Covid-19, a freedom of information response to Scotland on Sunday has revealed.
It raises the prospect of the structure remaining unfinished when it reaches its third anniversary in August.
Finishing and snagging work was originally due to have been completed in September 2018, just over a year after the crossing was opened to traffic.
This was later postponed to October 2019, then December 2019 – and now “spring 2020”.
The Scottish Government’s Transport Scotland agency, in charge of the project, has admitted a further two months’ work to finish all the remaining jobs was still required when it was suspended because of the virus-enforced shutdown last month.
However, this could be extended if social distancing is required when it re-starts.
A spokesperson said: “The majority of outstanding work was completed by December 2019, with three remaining activities expected to be complete this spring, during the period the contractor demobilised from the site.
“However, from 23 March, in line with guidance, all non-essential work was stopped to help tackle the spread of coronavirus. This work will now resume when it is safe to do so and will last for approximately two months.”
The spokesperson said a separate contract to install ice and weather sensors on the bridge’s cables should take one month, but was dependent on good weather.
They were ordered after ice damaged vehicles crossing the bridge, forcing its closure for two days in February.
Transport Scotland said: “Installation was planned to commence in June but if restrictions are still in place at that time, work will commence as soon as possible thereafter.
“We intend to have the sensors operational before next winter.”
Scottish Labour transport spokesman Colin Smyth said: “It is frustrating there were yet more delays over this apparently never-ending project.
“With work now rightly halted due to the Covid-19 outbreak and further changes likely to tackle the ongoing issue of closures caused by ice build-up, you do wonder when we will see a completed sign on the bridge.
“Nearly three years on from its opening, that’s deeply disappointing.”
Dean Lockhart, his Scottish Conservatives counterpart, said: “We keep getting told by the Scottish Government that works on the Queensferry Crossing have been finished.
“But here we have yet another delay to the completion of the works – which arose before the disruption caused by Covid-19 – meaning the official completion of works is now years overdue.
“It’s no surprise commuters are getting frustrated by these constant delays.”
Neil Greig, the Scotland-based policy and research director of the IAM RoadSmart motoring group, said: “It’s a pity, but fully understandable, that in the current lockdown all work could not have been completed when the bridge is so quiet.
“It is absolutely vital the new ice sensors are in place by next winter. For a bridge sold on its ‘resilience’ in all weathers, they were a major omission.”