investment property- FV model

sir as far as investment properties are concerned we would initially recognise them at cost and then subsequently choose to follow either COST or REVALUATION model. And as per IFRS 40this model/policy “must be applied to all investment properties”. Now, my question is that if after following FV model for long, if in some exceptional circumstance am unable to measure a certain investment property at fair value then does that mean I have to shift to cost model for all investment properties?

many thanks!