Generally FME determines that two string values match if they look identical, regardless of their data types. Could you please post minimal source datasets and a workspace that reproduce the issue?

The ChangeDetector (or tried Feature Merger) finds about 150 out of 4,500 known ID's (app_d) and owner1 field of interest, which are the same in 2 sets. The ChangeDetector uploads the non matching Insert data to the db. When I then run a standard SQL join Insert to existing data (the Revised data input from db to ChangeDetector) it nicely joins 4,5000 records, where app_d and owner1 are the same in existing (revised data) and Original