Entities do not appear in Dataflow when creating Linked Entities

I am having a similar issue, I could not create a new linked entity from a new dataflows Entity (which I created today).  I also lost an existing entity link.   It was a date table, however when i tried to load the dataflow containing a group of linked entities it throws an error complaining the original entity wasn't valid.

The best I can tell is Entity with a Date in it, will not longer appear for selection when linking.  The workaround suggested didn't help me.  I have 2 workspaces, one containing fact/dimension dataflows and anything will a date is problematic. I can see Dates are being stored as "Unclassified" for the data type.  To expand a little:

Workspace 1:  has 2 dataflows for building the entities.  Any field that contains a date field are now unclassified.

Workspace 2:  has 2 dataflows that link the entities from Workspace one.  I cannot see any Entities from Workspace 1 that contain a Date field.

When i try to link from workspace 1 to workspace 1 (just a test i wouldn't actually do that in the real world), I cannot see any Entities that contain a Date Field.  The new entity i created  cannot be linked and doesn't appear either and it contains no dates.

Last week I was having a problem with Date fields where being stored as DateTime (despite selecting "Date" as the type).  I am not sure if they have attempted to fix that, but this is a pretty big regression.  Essentially dataflows are now unusable. 

It is pretty bad if it is going to take 5 days.  I cannot raise a support ticket as I don't have the privileges to do it (my company has strict controls).  I would be interested if anyone else has these symptoms.

Doodle Make sure you do an edit the existing ones which work. If you make any change, the tables start to crash. Or may be save a copy of JSON from the dataflow if you need to do any changes.