Plateauing HCG

Has anyone had an experience in their first trimester where their hcg plateaus and then goes back to normal and continues doubling? My most recent labs show an hcg rise by 100ish but it should’ve been closer to 500. My doctor called and told me to come in tomorrow to get my labs done again but I’m wanting to be prepared? Is this common or is it inevitable that a miscarriage is coming?