Here is a fix for the following error message in VUM: "Invalid vendor code del in patch metadata, another vendor code with different capitalization already exists in database. Check the Update Manager log files for more details."

1. Unzip dell-eql-mem-esx6-1.4.0.426823.zip (or similarly named file)
2. Edit index.xml
3. Change line 4 (ie. code tag) from "del" to "DELL" (no quotes)
4. Zip all previously unziped files back into the originally named file.

I used the MEM 1.3 patch as a template and tested the modified MEM 1.4 on vmware 6.5.