Open lids thoroughly, check inlet and outlet baffles and tees, file fractures or corrosion

https://charlie-wiki.win/index.php/Hydro-Jetting_vs_Conventional_Septic_Tank_Cleaning:_When_and_also_Why_to_Utilize_Each

Open covers carefully, check inlet and outlet baffles and tees, file fractures or corrosion, and repair seals to stop groundwater intrusion and exfiltration that can overload the drainfield.