Experience the same issue on Stable 1.04.111746

Very simple MP mission with 3 units on the map, no scripts etc.
2nd unit config:

id=1;
side="WEST";
vehicle="B_Soldier_F";
player="PLAY CDG";
forceHeadlessClient=1;
leader=1;
skill=0.60000002;
text="Unit_2_hc";
description="Unit_2_hc";

Expected behavior:
HC will connect automatically in 2nd player slot

Observed behavior:

• HC will automatically connect to 1st available player slot and never in reserved hc slot

(This slot disappears from selectable players even if hc is dragged to other slot)

• HC will in most cases(?) not init successfully after mission start due to timeout.
• Manual drag to 2nd_hc slot of hc user is not possible
• Manual drag to 1st or 3rd slot of hc user is possible. After manual drag to any slot HC inits successfully and mission starts successfully

Removing "forceHeadlessClient=1; " from 2nd unit
Observed behavior:

• HC will automatically connect to 1st available player slot

(This slot disappears from selectable players even if hc is dragged to other slot)

• HC will in most cases(?) not init successfully after mission start due to timeout.
• Manual drag to 2nd_hc slot (or other slot) of hc user is now possible. After manual drag to any slot HC inits successfully and mission starts successfully .

In my rpt:

Cannot create entity with abstract type ParachuteWest (scope = private?)
Cannot create entity with abstract type ParachuteWest (scope = private?)
Cannot create entity with abstract type ParachuteWest (scope = private?)
Cannot create entity with abstract type ParachuteWest (scope = private?)
etc

I'm not aware of any specific A2 code used.