Using the last night build, I see some improvement as the last known focus position is correctly set when I use my Sesto Senso in a brand new Kstars/Ekos session. Which is great, thank you Jasem.
Unfortunately, a new bug has appeared (this is a regression compared to the last stable version I was using until today) : using the Indi Client board I have defined some preset values for that focuser. When I press the Goto button for one preset value, the Sesto Senso actually moves to that value, but that makes also the indi_sestosenso_focus driver crash. It is 100% reproducible. I attach the log file that shows the issue that is around these lines:
[2019-02-21T16:10:49.482 UTC INFO ][ org.kde.kstars.indi] - Sesto Senso : "[INFO] Device configuration applied. "
[2019-02-21T16:10:58.911 UTC INFO ][ org.kde.kstars.indi] - Sesto Senso : "[INFO] Moving to Preset 1 with position 0. "
[2019-02-21T16:11:00.113 UTC DEBG ][ org.kde.kstars.indi] - INDI Server: "2019-02-21T16:11:00: Driver indi_sestosenso_focus: terminate called after throwing an instance of 'std::invalid_argument'"
[2019-02-21T16:11:00.113 UTC DEBG ][ org.kde.kstars.indi] - INDI Server: "2019-02-21T16:11:00: Driver indi_sestosenso_focus: what(): stoi"
[2019-02-21T16:11:00.114 UTC DEBG ][ org.kde.kstars.indi] - INDI Server: ""
[2019-02-21T16:11:00.310 UTC DEBG ][ org.kde.kstars.indi] - INDI Server: "Child process 6843 died"
[2019-02-21T16:11:00.310 UTC DEBG ][ org.kde.kstars.indi] - INDI Server: "2019-02-21T16:11:00: Driver indi_sestosenso_focus: stderr EOF"
[2019-02-21T16:11:00.310 UTC DEBG ][ org.kde.kstars.indi] - INDI Server: "2019-02-21T16:11:00: Driver indi_sestosenso_focus: restart #1"