Thanks. I am on Windows 10Pro on both the new and the old laptop.
When I went back to 126.96.36.199 on the new machine it ran first time without any issues. Then, when I ran it the second time it refused, with the same issues that 188.8.131.52 had previously. I ran the MS compatibility trouble-shooter. In the course of that check I set Windows 8 as the last known trouble-free run (even though SGP has been running perfectly on Win10Pro on the old machine) and since then 184.108.40.206 has run consistently trouble-free. I have just gone on the website and upgraded again to 220.127.116.11 and there are no issues - runs perfectly.
So I think it must be something to do with the way W10 is set up on the new laptop. The old machine has W10pro with SGP 18.104.22.168 running fine and now the new machine has W10Pro with SGP 22.214.171.124 running fine (but with W8 settings).