My dog lies down in the street and won’t get up and no he’s not tired he just doesn’t want to go home

My 9 year old Bearded Collie goes on 4-6 walks a day and each walk is about 15-20 minutes. But when he gets towards the end of the walk he lies down in the middle of the street and won’t get up. A firm tug doesn’t work, we’ve tried a harness as well. If you pretend to go back the other way (away from our house) he gets up right away (but then he won’t turn around or he’ll just lie back down). He’s not food motivated so treats are useless.

Eventually he gets up but this could take 10 minutes of him just sitting there.

Any advice?