It is now 2015 and I am unfortunately having this same issue....I have a script that was created in Python 2.6 for 10.0 that runs, but are, yes I know, a little late, upgrading to 10.1 prior to going to 10.3 - moving right now is not an option....anyhow, a RemoveJoin works well with a shapefile, however there is one join in the script from the consultant that sets a join to a table in SDE. I have tried the same workarounds and still cannot get the RemoveJoin to work. Did anyone ever from up with a fix for this? Especially while working in SDE?
If you're using a table in SDE (instead of a feature class), are you creating a table view instead of a feature layer?
Also, make sure you're referencing the correct table view for the remove.
ArcGIS Help 10.1 - Remove Join (Data Management)
Could you also try rewriting just a simple add join, remove join based on the Esri help example to see if you're doing it right. Once you get something working, start adding in the rest of your code and see where it breaks. Maybe post a sample here so we can review it.
The consultant did not write the join table as such, only the feature class that the table was to be joined to. I did test two different ways…
I created a small model that made a feature layer as well as a table view, created the join, and then tried to remove the join. In addition, I exported the script out to test it, just to be on the safe side. The Remove Join still failed, and instead of giving an “800” error, it gives the infamous 999999 error (see below).
I just tried the same thing in a File Geodatabase and it worked. Maybe try leaving that optional "Join" field in Remove Join blank.
However, I was not using GlobalID as a key field. Is there something else you could use to test with just to see if you can get a model that works?