We did resolve a memory issue last year for a very specific scenario. It primarily only impacted solutions with a large number of providers in OnBase (the main customer experiencing the issue had over 150k). We updated SD4E to support server-side physician searching, so that the SD4E Client did not need to receive all physicians prior to launching. This helped significantly with memory usage, in addition to reducing launch times. However, this was only done in EP5/21.1 and higher. It is not something that can be backported further. If you do not have a large number of providers, this likely does not apply to your situation.
It is possible that whatever issue you're running into is no longer occurring in EP3 as it may have been addressed by other changes between those versions, as 16 and EP3 are 5 releases apart.
I hope that Kent's answer is more applicable to your situation, since the information I provided is only useful once you upgrade to/past EP5.
