Documents from Wiki and JDBC connectors are removed whenever the agents process is started when continuous crawling

"Indeed, when using the file system connector, Manifold works as it should. The agent can be stopped and restarted and the previously processed documents are retained. When I tried the JDBC (pointed to a MySQL DB) and Wiki connectors, however, I received the same results as yesterday - all documents are deleted as soon as the agent restarts (not on shutdown but when running the agent again after it has been stopped).

For the JDBC connector I could imagine that this may somehow be related to flawed seeding or version queries (although I believe them to be ok), but in the case of Wiki there are hardly any settings I believe I could have gotten wrong."