There occur to be four major manufacturers of serial to USB chips + STM32, which embed the serial interface in the CPU. There are also clones/counterfites of these.
One of these manufacturers is Prolific, there are several issues with their drivers, one of which is that (sometimes) after a device is unplugged, it is not removed from the registry.
This is one of the reasons not to get the list of the devices from the registry, but from a windows service (Win32_PnPEntity). In TSerialSelector this is named WMI mode and is switchable from the properties.
Also, when multiple devices have been plugged and unplugged in the same PC, their data is not removed from the registry. So there might be multiple data for one and the same COM and getting friendly names (and serial № if available) is not reliable. This issue does not exist with WMI mode.
About multiple COMs with the same name at the same time - I have seen it in the following ocasions:
1. Blue/black pill with USB set to keyboard/ mouse, but for some reason recognised by windows as a COM port. In this case there is an error shown in the device manager.
2. Virtual device of com0com.
3. Maybe (I am not sure that I remember properly, so I have some doubt) with some Prolific devices, usually this gets fixed when refreshing the device manager or rather reinstalling the driver.