Bad results printing with PLA

[jorgevgg 0]

 

 

Hi, 

I´m having some problems when print with PLA,

firstly the piece goes well but when it has built some layers, appear a defect of undercontruction, 

the amount of filament that is deposited is less than the neccesary, and at the end it seems that the error dissapear for the top layers.

 

Any  idea or suggestion why my ultimaker 3 is doing this?

Thanks in advance