So, it seems you might be breaking the Terms of service here.
The Forge is using resources for each world online, if you’re 2 GM’s Gm’ing at the same time, it breaks the terms. 
What should be done is have the second GM have their own server, it seems that would fix your issue.
In this case, your second GM shouldn’t need Admin access either. I’ll also inform that you break the terms by sharing your account.
Can I share my account with a friend ?
As per our Terms of Service , you can never share your account credentials with anyone. Even The Forge team will never ask you for your password and you should never give it to anyone. This is due to both security concerns as well as legal reasons. Your password is like your credit card PIN number, if you wouldn’t share that with someone, then don’t give them your password either.
You could however share access to games within your account with a sibling or your children for example. In the case of friends, if they are part of the same gaming group as you and they want to DM a game in which you are a player, then that’s perfectly acceptable for you to host the game as part of the Foundry VTT licensing terms and The Forge Terms of Service. This wouldn’t count as account sharing, but rather, you are hosting a game in which you are not the GM.
There are also campaigns of the West Marches style in which different GMs alternate with different players within the same world. That would still count as a single (albeit large) gaming group and is therefore allowed.The use case that is not acceptable is if two people playing in independent gaming groups decide to share the cost of a subscription because their groups play on different days of the week. That is both unethical and hurtful to The Forge service.
The Forge has created efficient software to keep costs as low as possible for the users of the service and part of that is the efficient handling of server resources which would be impeded by people sharing their accounts with other independent DMs or by preventing the regular idling of inactive games.
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