Ministers have revealed that a total of 13 of 23 tasks that were incomplete when traffic started using the bridge in August 2017 are still being worked on.
The latest update to the snagging list also shows eight of those have been delayed for a third time.
They include more work being required on road drainage and lighting, which was put back to March last year, then December, then “spring 2019”.
Scottish Labour condemned the delays as “totally unacceptable”.
But the Scottish Government’s Transport Scotland agency said there would be no extra cost to the taxpayer from the extra and delayed work.
Completion of all the snagging work is still expected in October – a date which has not slipped further in the latest update.
MSPs are expected to receive a further update next month.
The late-running work caused delays last year, but drivers have reported far less disruption from such overnight lane closures so far this year.
Work now starts later in the evenings after complaints about traffic queues.
Transport secretary Michael Matheson, in an update letter on progress on the bridge to the Scottish parliament’s rural economy and connectivity committee, revealed one of the new delays had been caused by a dispute between the Forth Crossing Bridge Constructors group (FCBC) building the crossing and a sub-contractor, Maspero.
It means the tower lifts will not now be finished until this summer.
The letter said: “Maspero abandoned the site prior to lift installation and FCBC have had to appoint a new supplier, Alimak.”
Another delay was caused by floodlighting having to be changed. “During commissioning, it was realised the below-deck system required a re-design due to a geometry clash between the lights and the under-deck gantries.”
Matheson also admitted “general finishing” was taking longer because there was “more work required than initially anticipated”.
Scottish Labour transport spokesman Colin Smyth said: “While some snagging was always to be expected, it is totally unacceptable that work to complete the bridge won’t be completed until more than two years after it opened to traffic and a year longer than Transport Scotland said all work would be finished.
“Commuters are getting fed up with the delays extra work often causes on a bridge that should have been finished some time ago. They simply won’t believe a word Transport Scotland say when they give completion dates.
“Serious questions need to be asked as to why this work is dragging on and why completion dates keep changing”.
Jamie Greene, his Scottish Conservatives counterpart, said: “The Queensferry Crossing is undoubtedly a great feat of engineering and a welcome addition to our road network, but one does have to ask why so long after it opened with such public relations fanfare there remains a mammoth list of snagging works. Questions remain as to why they are taking so long to complete the work and did the transport minister know there was such a backlog and delay to finalising works on the bridge?”
A Transport Scotland spokesman said: “It is of course very common for major projects to open to traffic whilst some works remain outstanding. We have no concerns that any outstanding snagging items will compromise the life of the structure, and these works will be completed at no additional cost to the taxpayer. Our contractor, FCBC, is progressing finishing works and they are scheduled for completion later this year.”