If your current capture process can’t keep up with the traffic and drops packets – you need a new capture process. No debates here. Analyzing a trace file in which you don’t have all the packets of interest will waste your time. You aren’t seeing a true picture of the traffic, and, when you analyze the trace file in Wireshark after the capture, you will likely see the ‘Expert’ complain about problems which don’t actually exist. There is a solution, and you may not even realize that you already have it: Tshark!
When you installed Wireshark, you likely also installed a set of command-line interface (CLI) tools into the Wireshark program file directory. One of these CLI tools is Tshark. Tshark can be used to capture and analyze traffic. It offers more functionality than the standard tcpdump and may become your go-to tool to grab the right packets from the network.