Richard,
Thanks for your message.
Indeed, updated the TWS to the latest standalone stable 10.19.2m gave me some blessing.
Weird since I kept checking the latest self-updating TWS (10.29.1g as of now) and the "Never lock" option is still missing there.
Point taken about messaging the CS team at IB, but they are still working on a bug I have reported last year.
So they aren't that quick.
Nevertheless, have a good day.
whatrichme