EEA FP to Residence Card

Hi,

Someone from another post told me that the EEA FP is only valid for 6 months and afterwards, my family member will have to apply for residence card in UK. I would like to know if EEA FP has been granted and my family member entered UK and apply for residence card, will they subject for checks or further checks by HO or getting a residence card after EEA FP is just a formality and matter of processing time?

Thank you,