@ Dwammy

• I have re-installed v1.7 from my existing files, no luck.
  I have done a reapair from my existing files, no luck.
  I have uninstalled all and re-installed from my existing files, no luck.
  I have uninstalled, cleaned all remanents left behind and re-installed from my existing files, no luck.
  I have uninstalled and cleaned again, re-downloaded all the files (all AV off) and installed again, no luck.
  This evening, I uninstalled again, cleaned again and re-installed one at a time, checking in the Sim each expansion to see undercarriage showing and a large percentage of models for correct flight controls.
  All seemed to be working and in good order, untill..... I finally installed the Freighter Essentials expansion and now I have lost the undercarriage on a number of models again, I hope this may be a clue (?)