teething troubles 
(also teething problems)
plural noun
Short-term problems that occur in the early stages of a new project: the inevitable teething troubles of a new system...
- But he said the problems were early teething problems connected with the new finance system.
- But these are early days and such teething troubles should be forgiven in this first collaboration between two great art collections.
- The Scottish parliament is a good idea, but has had the inevitable teething troubles which one would expect at the initial stages.