Concordance reverse TM with AnyTM

Hello,

I translate both from NL into FR and from FR into NL, and I often need to translate parts of documents that I have translated earlier (sometimes in the other language direction).

I know how to use a TM correctly, but in this case, I would really need to be able to use both my memories NL=>FR & FR=>NL in both directions. 

So for instance, for my project "NL=>FR", I have added the TM "NL=>FR", but also the TM "FR=>NL" under AnyTM in order to create a reverse TM, as I have read online this was possible. However, the problem is it looks like I am not able to use the concordance from this reverse TM (even though "look up" is supposed to be active). I know that for sure because when I get a translation the other way around, sometimes it will not give me any TM proposal or find anything in the concordance even if the translation segment is available in my TM in the other language direction... am I doing something wrong here or using TMs the wrong way? I know there are some plugins to do this... but I don't want to just create a reverted TM from a .tmx, as I want to be able to use both TMs in both directions in a version that is up-to-date all the time. Also, I have noticed an option in my 2017 Studio version, it is asking me to upgrade my TMs every few days... not sure what this feature is indented for and if this has anything to do with updating reverse TMs as well.

Hoping my question is clear.

Thanks a lot in advance.

Best regards,
A.L.