Test VBox: very frequent "IVirtualBox object is null" + "failed to connect to test machine"

[SYSREG] sysreg2 r2334 starting

libvirt: VirtualBox Driver error : internal error: IVirtualBox object is null

[SYSREG] Error: failed to connect to test machine.

[SYSREG] Status: Testing process aborted!

program finished with exit code 2

—

https://build.reactos.org/builders/Test%20VBox?numbuilds=200

6624, 6626, 6628-6629, 6631, 6635, 6651, 6654-6655, ...

While CORE-14227 existed (6689-6784):
6690-6691, 6693-6696, 6698-6701, 6703-6706, 6708-6711, 6713-6716, 6718-6720, 6722-6723, ...
Iirc, failed to connect is the main point, though the detailed cause is rarely/sometimes different!?

6786, 6792-6793, 6796-6799, 6802-6803, 6805-6806, 6809-6811, 6813-6814, ...