Ecgs bushing question

So i think I found where the knock is coming from.i checked the cam bolt torque numbers and all are good . So i decided to check the drivers side axle shaft for play and what I found is that there is play in and out and about a 1/8 of an inch up and down at the differential. I did the ecgs bushing last summer do you know if it' common to have up and down play in it again after installing the new bushing after some time of driving with it