Scanning Or Pinging Computer Name Not Found Now

I don't think this is a PDQ problem, but it happens when I scan with PDQ Inventory lately. I am hoping that other PDQ users have seen this and can point me in the right direction. We are setup/using IPv4 throughout.

I used to be able to just ping local computers by name and get a response. Now when I scan via PDQ, I get an error that "Computer name could not be found" on some Windows 10 clients. I can ping the IP address OK. I can issue "ping -4 <computer_name>" OK. I can add the name to my host file and can ping by name OK.

Why can I not ping these clients by name without forcing IPv4? I have disabled IPv6 in my network settings to test.