A project to repair a bridge, which was supposed to last six weeks and be completed a year ago, will now drag on until April.
There have been traffic problems since the work on Roding Bridge, which links Buckhurst Hill and Chigwell, began in December 2012.
Vandalism and accusations of delays caused by utility companies have previously been blamed for problems completing the work.
But now Essex County Council says engineers have discovered the new section of the bridge is not properly supported as the structure is only submerged in the river bed by one metre.
Councillor John Knapman said: "It has already been over a year since traffic was limited to a single lane causing misery for our residents.
“While this new problem has to be addressed, the whole matter seems to have been beset with project mismanagement issues and a lack of urgency.
“I will be calling for an investigation so that others do not have to go through the daily delays which have affected those trying to get to work and to school particularly badly."
Cllr Valerie Metcalfe representing Buckhurst Hill and Loughton South, said:"There has been a major problem between Essex County Council and the Utilities Companies which took far too long to resolve.
“We had been promised that the bridge would be operating fully by summer last year. Since then the date has been pushed back again and again."
Utilities companies have denied causing delays, claiming agreed payments were not made on time by Essex County Council.
The Guardian is awaiting a statement from the authority.