@Bastien Montagne (mont29) HI sory but how ?-? this could be posible to describe this in other way (i already reported some bugs when i use video as addisional help) ? I mention CTRL-Z becouse i found that conected with this error. Short video max20 sek with clear view of what i'm doing from opening file to error without any unnessesary steps. Of course i try recreate that with simple cube or ecosphere bit i failed so i have to report with this complicated to analize model. I WILL be better next time with more precise description of the error. Thank you all for your work.

I found the way how to overcome that. For example ... if i want to get to leafs UV i have to mark one vertex then enable "show faces". Next mark everyone by "A" and here we go.

ps: If i save file after bug ( i try it with last i manege to create in video ), blender try to conect broken vertexes

Interesting ... sorry for late respond. I use mause and again, ( i update blender too... ) all you have to do is follow what i done on this video... spin that "thing" to see neck area and just swing a few times your mause. I done this again within 10 seconds. It works barely always. And no i only sculpt on this clay strips brush ... i can't trigger that nasty glich with other brushes.

Hah.. I found how to reproduce another bug on the same blend file ( diferent pc laptop, same blender version ) ASUS K550V i5 6th gen. and gtx 750m
reproductable. Sorry for voice but I had to be quiet then.