Npcap is the preferred Avanti network backend and normally permits the Windows host and an emulated NIC to use the same physical adapter.  See PCAP Drivers for the current backend guidance.

Historical field reports associated some Windows adapter and driver combinations with poor throughput, retransmission, packet loss, and a Tru64 UNIX 0x670 machine check while the host and guest shared an adapter.  Those reports were not reproduced across the supported Windows range and do not establish that sharing is generally unsafe.

If the exact symptom is repeatable, first record the Windows adapter, driver, packet backend, guest NIC, and traffic direction.  Then test a dedicated wired adapter as a diagnostic isolation step.  Retain the dedicated layout only when it corrects the recorded case; it is not a general Avanti requirement.