Council roading projects engineer Michael Harrison said the problem meant contractors were having to excavate to a greater depth than planned as work continued on a new retaining wall designed to fix the slip.
The slip occurred when a storm undermined a section of Portobello Rd at Turnbulls Bay in mid-2013.
Repairs finally began in January, but struck trouble last month when a 15m-long crack along the road opened up at the site on February 24.
The crack, together with extra slipping, meant traffic had to be diverted through a nearby car park to avoid the site.
Despite that, Mr Harrison said yesterday it was ''business as usual'' for contractors, who were continuing to work on foundations for the new retaining wall.
There had been no significant change to the design or timetable of the project, which was still due for completion in May, he said.
However, the extra excavation required for the retaining wall's foundations would mean additional cost.
Fuller information would be made public once that became available.
