Thanks. Yes I didnt explain well.

No, I've not tried multi sig.

I think the problem was that the wallet on machine 1 with a more recent blockchain could see that several addresses had been used to receive coins. So it had hidden them from view as recieve addresses. Machine 2 with a older copy of the blockchain didnt know this so was generating them as new receive addresess. So it looked at first like they were not generating the same sequence of addresses

So it took a few more clicks on both until I reached an address that had never been used to receive coins.

They are now both creating identical addresses in the same order on both machines.

I wasnt aware bitcoin core hides receive addreses once they have been used.