I have the 320 an 220 an all the 10 collars on both of the units the 320 will pick up all 10 collars an the 220 will pick up half sumtimes jus one collar.. The kicker is the 220 picked all the 10 collars before adding the collars to the 320... Not sure what the problem is.. Thanks for any info

check see if your id numbers show up same for each collar on both units

Thanks a couple of the collars had different id numbers thanks again