The latest updates of Microsoft Defender Antivirus cause slowdowns (lag) of up to 4 seconds for MB STUDIO operations. It is therefore essential to add the MB STUDIO folder to the antivirus exclusion list.
Follow this procedure: https://support.microsoft.com/en-us/windows/add-an-exclusion-to-windows-security-811816c0-4dfd-af4a-47e4-c301afe13b26 and then select the MB STUDIO folder which is usually C: \ MBStudio.
There is no need to restart MB STUDIO or Windows.