Every case has a priority date (mentioned on your NOA). This is the date based on which USCIS processes and takes decisions. The other factor is the 5 yrs continous residency based on employment and 3 yrs based on marriage. Whichever category you fall into, until you have completed the required tenure, the interview activity does not start. Thats what everyone mentions in the forum.
To conclude, though your FP got delayed, your Priority Date still remains the same, so you're good to go.
It seems who ever files under 5 year rule, USCIS may wait for some time prior to scheduling interview even after FP check complete