This is an intermittent error, which affects only some machines. It has become much more frequent since the release of Trados Studio 2019 SR1 and MultiTerm 2019 CU1. A number of events come together to cause it, and the easiest way to attempt a fix is to run the repair tool that is available on the Glossary Converter website.

Since the causes are still not exactly clear, there is no guarantee it will work, but a good number of errors were fixed. This handles the known 2017/2019 problems, it's not suitable for other versions. 

Another fix was reported that helped particularly when older versions of MultiTerm/Trados were used: try the older Glossary Converter, build 5.1. It is still available on the Glossary Converter website

If you can't fix it, there is a workaround:

• Use the Glossary Converter to create an xdt/xml file pair
• In MultiTerm, create a new termbase based on the xdt
• In MultiTerm, import the xml file