Couple ideas...you may want to pour mineral spirits into the oil pan, scrub the inside best as you can with some cheapee flexible long handle brushes thru the front opening of the pan that will be exposed. Drain it, maybe repeat and pour more spirits thru and see what comes out. Sludge, possibly nylon cam gear teeth. Wire an extension to the brush handle to get way down to back of pan, maybe a coat hanger. Also fill a dish soap or equivalent Flip top bottle with spirits and shoot it thru the oil hole in block pictured. It may help back flush your oil pickup screen, since you're probably not removing the oil pan.