Step 1) Launch Steam
Step 2) Launch Arma Reforger
Step 3) Select Multiplayer
Step 4) Host New Server
Configure Server for any custom settings.
Step 5) Map - Select any "conflict" mode map.
Step 6) Build Armory
Step 7) Build living quarters "300 resource"
Step 8) Purchase any squad
Step 9) Use "~" to order squad around (Works great!!!!)
Step 10) Have a friend, or anyone join as the 2nd player (Steam PC) in your faction
Step 11) "~" Squad Command key stops working (Life Sucks!!!!)

• DETAILS: As soon as my group member/friend joins the server either same squad, or creating his own squad "~" key stops functioning.

Upon each keypress "~" the white menu mouse cursor appears briefly, and whichever item you were holding (IE: 1 Weapon, 2 Secondary weapon, 3 bandages, 4, 5, 6, 7, 8, 9, 0 entrenching tool) for arguments sake lets say I had my entrenching tool equipped slot "0".
Each keypress of "~" white cursor flashes, and then held active item Quickbar icon appears.

I have tried assigning long "hold", multi-keypress using ALT, CTL, SHIFT, and the 6 million permutations / combination of alternative keys on the keyboard and the problem persists.

I am willing to reproduce and show this bug to the developer, via streaming in Discord.