Problem is that I have no HC but I observe what is reason of this situations - dummies units prepared for players JOIN to them, blocked AI units are connected to them and dedicated still see them as players (why ??). This problem happen when players unconnect from server unexpected and dedicated not allow to change their locality ot any other client.

Using setgroupowner not work too - anyway using this command on new unit joined to group of player  (client) have no sense, beacouse join group should chenge locality of this new unit in moment of join (player's group) isn't it? I think my problem and not only mine regards to some strange non player AI units, ready for JIP and seen by dedicated as players anyway - the AI units in those goups are immortal and undelatable from console or zeus, and of course blocked form locality change.

The problem is on interpretation of dedicated some AI units ready to join players on them - when players unconnect unexpected those units are seen by dedicated server as dummy players and all AI unist connected to them before player unconnect are blocked from all those commands (this#0) is just from add action form (as you can se below), before this is used join group ets here is whole command for join AI man unit and vehicle with AI units inside (example below it work in most cases perfectly just after unconnect players it stuck) and all those AI seems to be remote forever and all setowner and setowner group commands return false.   //unit join                     private _idact_next = _x addAction ["<t color='#FFFF00'>" + localize "STR_JOIN_TO_GROUP" + "</t>",{[(_this#0)] join group (_this#1);[(_this#0),clientowner] remoteexeccall ["setOwner",2,false];dostop (_this#0);if (!(captive (_this#0)) && (((_this#0) getvariable ['SIDE',CIVILIAN]) != game_side_enemy)) then {(_this#0) enableAI 'all';[(_this#0), ([(_this#1)] call BIS_fnc_getUnitInsignia)] call BIS_fnc_setUnitInsignia}else {[(_this#0),remote_call_prisonner] remoteexeccall ['spawn',2];if (lifeState (_this#0) != "INCAPACITATED") then {(_this#0) enableAI "ANIM";(_this#0) enableAI "MOVE";dostop (_this#0);[(_this#0),"AmovPercMstpSsurWnonDnon_AmovPercMstpSnonWnonDnon"] remoteexeccall ["switchMove"]}};(_this#0) call AI_group_change},nil,-850,true,true,"","(vehicle player == player) && (side _target != sideEnemy) && (lifeState _target != 'INCAPACITATED') && (((_target getvariable ['SIDE',CIVILIAN]) != game_side_enemy) || (captive _target)) && (group _target != group player) && (alive _target) && !(_target getvariable ['CAPTURED',false]) && !(isplayer _target)",_actionmanrange];
                    _x setvariable ["action_JOIN",_idact_next,false];   //vehicle join                       private _idact_next = _x addAction ["<t color='#FFFF00'>" + localize "STR_CAPTUREVEH" + "</t>",{(_this#0) lock 0;[(_this#0),clientowner] remoteexeccall ["setOwner",2,false];{if (!(isplayer _x) && (!(_x getVariable ['GRP_CHANGE', false]) || !(isplayer leader _x)) && (alive _x)) then {[_x] join (group (_this#1));[_x,clientowner] remoteexeccall ["setOwner",2,false];[_x, ([(_this#1)] call BIS_fnc_getUnitInsignia)] call BIS_fnc_setUnitInsignia;[[_x],AI_group_change] REMOTEEXECcall ["call",[0,-2] select isDedicated,true];_x enableAI 'all'}} foreach (crew (_this#0))},nil,-850,true,true,"","(vehicle player == player) && (side _target != sideEnemy) && (group _target != group player) && (alive _target) && ({!(isplayer _x) && (!(_x getVariable ['GRP_CHANGE', false]) || !(isplayer leader _x)) && (alive _x) && !(_x in (units group player))} count (crew _target) > 0)",10];
                    _x setvariable ["action_JOINVEH",_idact_next,false];   if setowner is not for that what is? (setowner group not work in some cases so good (even if this warning message is shown about setownergroup)), anyway problem is on other thing (unconnected player's units). So question still active what are circumstances for block AI units from change their locality on dedicated - and return false?

Yes

https://apnews.com/article/army-special-forces-troops-cuts-ukraine-lessons-ac7c41d5d9f299fadc96f2c2520c2abf?fbclid=IwZXh0bgNhZW0CMTAAAR3sZaUPjS6asM7YAkxGh8hV45oy6rB4SWMliFGMMRnBkctVZJK0YcCvBCs_aem_Aa0ytdTyhlIFFGXf7ihkP-xA2nYikoiAcBGT0YCGvTengfnELz69YvkUnysWKZyAg8AnTzF5U3Mq98PAXMPu-1mU#:~:text=(AP) — Forced to do,over the next five years   Going to keep an eye on this for the MH-60M and the MH-92F Insertion birds. If it comes to it I think I can add thrree more proxies for a fifteen-man team in the passenger area. But as said if it comes down to it I'll see what I can do within the Armaverse too.