Hello @Olivier Chénot
You may try configure the policy value for Computer Configuration -> Administrative Templates -> Windows Components
-> Remote Desktop Services -> Remote Desktop Session Host->session time limits.
And also please follow below link to setup simultaneous Remote login for multiple users:
https://community.dynamics.com/365/b/dynamics365enterprisecloudfronts/posts/setup-simultaneous-remote-login-for-multiple-users
Let us know if further assistance is required.
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Best Regards
Karlie