https://support.sophos.com/support/s/article/KB-000037007?language=en_US
Where we are instructed to type:
tcpdump filedump 'host x.x.x.x -s0
an error is produced.
tcpdump: can't parse filter expression: syntax error
What I did was to type
tcpdump host x.x.x.x -w /tmp/data/test1.pcap
This successfully write the file.