Strangest bug ever?

I just created my forth team and I'm haveing a VERY strange behaviour. I don't know if this is due to that my previous character sets were made in build 38 and the new set is made in build 41 as I never had this problem before.

The problem is that characters 1 & 2 will not work with each other. 1-3-4-5 and 2-3-4-5 works fine together (nothing works when sent 1-2 or 2-1)

Example:

I'm on Slot 1, I press the follow key. 3-4-5 follows, 2 open bag (!)
I'm on slot 2, I press the follow key, 3-4-5 follows, 1 puts a purple raid marker on a target (!)

How do one find the error here? I'm absolutely a big "?".

Facts:

I have 3 other working teams.
I have tried deleting and remaking the team.

Is there any way I can get the old client and try setting up the teams there cause in build 38 it seems to work fine for me.

[lax]

38 uses the same follow and assist keys and you would see exactly the same behavior.

When you're in Slot 1, and you press your Follow hotkey, it sends Left Shift+F11 to the other windows. If window 2 opens a bag, then most likely that window has the ISBoxer Addon disabled and the Shift+F11 macro is not available, so WoW interprets it as F11 which opens a bag. I would go to the Character Selection screen in that window and click on Addons and make sure the ISBoxer Addon is enabled.

When you're in Slot 2, and you press your Follow hotkey, it sends Right Shift+F11 to the other windows. If window 1 puts a purple raid marker on the target, then most likely that window either ALSO has the ISBoxer Addon disabled... OR... has a key binding configured in the game for Shift+F11 to put a purple raid marker on the target. Un-binding the Shift+F11 key binding within the game should restore your ability to make him follow.

(Reverting to 38 will change 0% of this)

This is also covered by the WoW Quicker Start Guide: WoW Quicker Start Guide, Part 6: Follow