Problem after Problem - Dyanamic Lux

One simple thing to try is see how things go with using CommandShift for a while (or at least from a standing start). Using CommandShift should bypass any "learned" shift pattern. This really does sound like a mechanical rather than an electronic/computer issue to me.

I'd forget about chipping the ECU as it's a sure fire way of JLR not doing anything at all to help you.

I think what you really need to do is demonstrate this in person to a service manager or mechanic.

Im gonna mention my recent DPF fault which we all expected to be a faulty sensor, It turned out to be a 'split DPF pipe' which was rectified much cheaper than an actual sensor replacement.