My understanding is that 1 a/c has been found to have problems and the others need to be checked before being returned to service if they are clear of the problem.
Let us hope that the problem is not fleet wide and is restricted to one a/c, which would at least be manageable and not give widespread disruption to the passengers.
I am not going to say what the problem is as I haven't the basic engineering knowledge to describe it properly, and there is enough exaggeration on here already!!