After switching to full-screen the system becomes unstable

[kalpana]

After switching to full-screen mode on Oracle VM VirtualBox, the system becomes unstable.
Code:

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hubble@main01:~$ lsb_release -a
No LSB modules are available.
Distributor ID:    Ubuntu
Description:    Ubuntu 22.04.2 LTS
Release:    22.04
Codename:    jammy
hubble@main01:~$ VBoxManage --version
6.1.38_Ubuntur153438
hubble@main01:~$
I have the Guest Additions installed.