In reply to Blodwyn:
I’ve have been using SLs for some 40 yrs. Most I’ve had have had some heel lift to start with.
As others have said lacing is important, and getting that right makes a big difference. I also have found that some replacements needed more breaking in than others, including my last activ model somewhat surprisingly. However, once shaped to my feet and with lacing sorted, they have all been comfortable.
I’ve never needed to change the footbed, but it all depends on foot anatomy, gait, etc. A good shop should help with ongoing fitting issues after selling the boots.