Count fails when joining more than two tables

[LangeJan]

I want to compare the contents of two tables 'Actual' and 'Estimate'. 

I compare by making a count of number of itemid´s in 'Actual'

NumberInActual = COUNT('Actual'[itemid]) +0

My count works fine when I only have content from two tables 'Actual' and 'Estimate'.

But when I include content from a third table 'MetaData', my count fails. 

Can anyone help me with a solution? 
Please let me know if any other information is necesary. Thanks

[amitchandak · Accepted solution]

@LangeJan , I think "no of pages" is no summarized, If that is column check for aggregation

[LangeJan]

@amitchandak Thanks,
I get the same error if I add one of the other coloumns from the 'Metadata table'.
Its like I dont have a uniq relation when I add the column "no of pages".

[LangeJan]

@amitchandak You are absolutely right, Thanks
I changed the "no of pages" from aggregation to number.