Unexpected packet loss on 10Gbps NIC even under low traffic (~10Mbps)

I'm experiencing unexpected packet loss on a 10Gbps Intel NIC (ixgbe driver) even when traffic is only around 10Mbps. The setup is a test environment using tcpdump to capture packets on Ubuntu 22.04 with kernel 6.2.0. Of course, I replaced cable, nic port (I used another port), nic but the result is the same. ### Observations: - Traffic generator sent 46,759 packets. - Only 37,676 packets were captured by tcpdump. - ethtool -S shows rx_dropped: 7 and rx_packets: 37,676. - tcpdump reports: 0 packets dropped by kernel. - NIC driver: ixgbe, firmware 1.808.0 - rx-usecs is set to 20, RX ring set to 8192. - RPS enabled: echo ffff > /sys/class/net/ens4f1/queues/rx-0/rps_cpus - IRQs are spread: all affinities set to 0-31 - NUMA node for NIC is 0, CPUs in node0 are 0-13,28-41. - /proc/softirqs shows NET_RX is active on multiple cores. ### Tried so far: - Reloading ixgbe driver (modprobe -r ixgbe && modprobe ixgbe) - Increasing RX ring buffer (ethtool -G ens4f1 rx 8192) - Disabling ntuple filtering and re-enabling (ethtool -K ens4f1 ntuple on) - Enabling rxhash (ethtool -K ens4f1 rxhash on) - Testing different rx-usecs (20, 50, 100) - Ensured IRQ and RPS distribution ### Questions: 1. Could the NIC drop packets even if rx_dropped is low and no kernel drops are shown? 2. Is there any known ixgbe behavior or firmware bug that could cause packet loss in such low load? 3. How can I confirm whether packet loss is really happening at the NIC or somewhere else in the kernel path? Any suggestions on further debugging or known limitations would be greatly appreciated.