One of the clearest examples of process tracing I have seen is in political science. Jakob Hauter (2023) analyses open source evidence concerning the 2014 occupation of Sloviansk and Kramatorsk in Donbas, to test the extent to which State actors were involved.
Hauter, J. (2023). Forensic conflict studies: Making sense of war in the social media age. Media, War & Conflict, 16(2), 153-172.