Please attach an example pcapng so that I'm able to reproduce it. You can use tshark to find the ESSIDs.
Example:
You captured test.pcapng
Now run tshark
$ tshark -r test.pcapng -T fields -e wlan.ssid | sort | uniq > essids.tshark
Than run hcxpcaptool:
$ hcxpcaptool -E essids.tmp test.pcapng
Sort the list:
$ cat essids.tmp | sort | uniq > essids.hcxpcaptool
Compare both:
$ diff essids.tshark essids.hcxpcaptool
if essids.hcxpcaptool contains less ESSIDs than essids.tshark, zip and attach the pcapng file here.
Example:
You captured test.pcapng
Now run tshark
$ tshark -r test.pcapng -T fields -e wlan.ssid | sort | uniq > essids.tshark
Than run hcxpcaptool:
$ hcxpcaptool -E essids.tmp test.pcapng
Sort the list:
$ cat essids.tmp | sort | uniq > essids.hcxpcaptool
Compare both:
$ diff essids.tshark essids.hcxpcaptool
if essids.hcxpcaptool contains less ESSIDs than essids.tshark, zip and attach the pcapng file here.