Can confirm ground testing passed well.
FW 1.3.20+
DJIGo v.3.1.18
FCC engaged and system will not prompt for WiFi change any more. What bothers me a bit is as what happens during checking distance through my apartment walls (much better results - obviously FCC is engaged). After loosing and reestablishing communication (just a second or two is enough), system immediately recognize wrong regional settings and wants to revert to CE. I wonder is this gonna happen in the air? I strongly believe it shouldn't because of the security reasons, but tests will show.
For now, I am more than happy with the results.
Home point and all other flight parameters looks as they should.
Looks like DJIGo 3.1.23 will not work. I tried with other mobile phone and it will immediately recognize wrong regional setting.
Switched back to 3.1.18 (left RC and drone left ON), and regional setting pops up again.
Turned off and back RC (drone left ON), no problem with regional settings.
My conclusion would be, once set to FCC no matter what drone "thinks" about region, important is how RC communicate with DJIGo regarding regional setting. Also, if wrong regional settings appears I believe it is necessary to turn off RC and that shut down DJIGo app (force to stop), without pressing OK on popup window.
Can't tell nothing more before flying tests...