Metabolite name conversion not 100%

This is an FYI.
The conversion, overall, is working, but for FUMARATE the output is GLYCEROL.
The two compounds are not identical.
Fumarate is KEGG C00122, whereas Glycerol is C00116.

I tried the conversion multiple times, with just 25 metabolite common names; the other names were converted to KEGG IDs (for use with with no problem.