The project was nearing completion in June 2024 when a crack appeared.
This was initially thought to be caused by settlement and not necessarily serious, although work was suspended for a time to allow the settlement to run its course.
Work then resumed last summer but the following autumn, a second split appeared which was caused by slippage of a body of material away from the rest of the earthwork.
This raised concerns over the integrity and safety of the structure and the project has been suspended since then.
Now, investigative work is underway to determine the cause of the project's failure, overseen by an experienced geotechnical engineer jointly appointed by Broxtowe Council and contractors Fox Owmby.
John Scuton, FOBV chair, said: "This work and subsequent testing of the extracted materials will take some weeks to complete.
"The same geotechnical engineer will prepare a revised design for the repair of the ramp and to make it fit for purpose."
While the ramp project remains on hold, Mr Scruton reported that work to build the new visitor centre at the site is continuing with the new building's roof now watertight and the floor screed is now being laid.
However, he said the remedial works to the ramp may delay the building of the car park and completion of phase two of this project.
He said: "Trustees are keeping a close eye on all parties involved in this project and pressing them where appropriate.
"The trustees apologise to all volunteers, members and the public for the further delay to the completion of the project and thank them for their patience.
"Trustees believe it will be well worth the wait for Bennerley Viaduct and its future.
"As we are at a critical period for the charity, the board would welcome expressions of interest from anyone who would like to become a trustee, especially people with business or hospitality experience."
Anyone interested should visit bennerleyviaduct.org.uk
In the meantime, further repairs and maintenance to the Iron Giant have also been carried out by Railway Paths Limited (RPL), the viaduct's owners.
At a meeting between the trust and RPL, Paul Thomas from RPL explained what they had done at the Grade II-listed structure and answered questions from FOBV members.
RPL’s biggest structural concern for the viaduct is erosion caused by the river Erewash.
This is also an issue for FOBV and plans are in place to prevent further erosion.
But it is a big-budget item and not something volunteers can do as there are strict guidelines and regulations to follow as set out by Historic England.
In the meantime, RPL has carried out some repairs and maintenance at deck level and on the wrought iron piers.
On the deck RPL has trialled placing zinc plates over the corrosion on some trough ends.
On the wrought iron piers RPL initially attempted to replace broken bolts and rivets but they could not remove the old ones which were fused in place by corrosion.
The engineers decided that drilling through could damage the structure, so they made brackets for those places where the ironwork is held on by just one bolt or rivet
Mr Thomas said RPL were open to other suggested improvements, provided FOBV can fund raise to help meet any increase in cost.
Suggested solutions will need to be approved by RPL and then trialled.
Any solution to the problem must be removeable to comply with Historic England requirements.