How to Read Two DOORS Databases into One RPE Template

I am trying, unsuccessfully to create an RPE Template to read data sources from two different DOORS Classic databases.

I have tried the Schema Discovery both with DOORS running and opening new DOORS instances.
I am able to create the schemas if I use DOORS running and open one database at a time, however teh document generation aborts.

When I use the schema to open a new instance of DOORS RPE will open the DOORS database but then just sits at the Reading data from DOORS pop up, before hanging.

I'd appreciate any help on this, Googling does not produce any results.