Symptoms
A DRDA Service exception occurs when there's a violation of the PRIMARY KEY constraint.
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Resolution
This issue is fixed in the following cumulative update for Host Integration Server:
Cumulative Update 5 for Host Integration Server 2016
Cumulative Update 1 for Host Integration Server 2020
References
Learn about the terminology that Microsoft uses to describe software updates.