The award-winning refurbishment of Wells Coates' Grade-I listed masterpiece was officially unveiled in July, but the euphoria has been dampened by reports of mould, floods and draughts.
Although the building's owners, the Notting Hill Housing Association, maintains the defects are just snags that can be fixed, some tenants are not convinced.
Andrea Breninek, a psychologist for a community health unit, moved into her flat in June and has been beset by water leaks which have caused her floor to blister.
She said: 'I don't think this is a minor problem. The Notting Hill Housing Association should wake up.
'My floor is still wet between the linoleum and the concrete and there's a huge damp spot on the stairwell. [The tenants] are worried there are a lot more problems underneath.'
She admits that the when she first moved in the flat seemed ideal. However, that soon changed. 'At the beginning when I moved in I was over the moon to have my own space,' she said. 'But then I noticed a few smaller things. When I saw the first spot of mould I started to panic. From then it became a nightmare.'
She added: 'I'm German and was brought up with Bauhaus - simple design and good workmanship. But at Isokon that has been turned on its head.
'The workmanship has been left behind.'
Breninek is particularly worried that once the 12-month guarantee - provided by builder Makers - is up she will be left to pay for any repairs herself.
'The guarantee runs out in December and in three months' time, [the association] won't have to do anything about [the defects].'
Breninek is not alone. Another resident who claims rainwater floods her flat has now written an anonymous letter to the local newspaper arguing that the association is 'not liaising with tenants to facilitate remedying defects.'
The AJ also understands that the tenants are intending to set up their own residents' association at the Lawn Road building to represent anyone with 'similar problems'.
However James MacPherson, the director of Notting Hill Home Ownership, is playing down the troubles, stating that the number of defects reported by residents is about average for a 'new building of its size'.
He said: 'We understand that there have some building defects at Isokon. The defects that have been reported to us, while annoying for the residents, are not major issues in terms of the building as a whole, that is to say, there is nothing substantially wrong with the building or the way it has been refurbished.
He went on: 'Any new or refurbished building will have defects - the defects at the Isokon are still under guarantee and we are confident the contractor will make good before the end of the defects period.'
He added: 'As the owner of the building we are very keen to ensure that the property remains in good repair - this includes the internal fixtures and fittings. We are sorry if any resident has been inconvenienced by the defects at their flat, but, as we have explained, this happens with any new building.
'We will ensure that the contractor maintains regular and productive contact with residents that have flat defects.'
Meanwhile John Allen, of Avanti Architects, who masterminded the refurbishment, said he was unaware of any large-scale problems. 'If somebody has a problem with a faulty washer then I'm not going to disagree,' he said. 'We were there on the Open House day and the whole atmosphere was very upbeat.'