flashing start light kenmore tried everything

intermitant stoping during washcycle reset starts again but not always
found plastic in drain motor
replaced drain motor pump
replaced tub thermostat
replaced circuit board
replaced door latching assembly
replaced thermister turbidity sensor
checked door switch
checked float switch
checked level
checked for drain blockage
checked upper thermostat
checked fill valve
checked conductivity of heating element

Called local whirlpool kenmore dealer had their recomended service guy come to fix . he could not find the problem $100. Prior experience with commercial appliance repair and have the tools. WHAT NOW PUMP MOTOR