When selecting Adjustable Ring Hangers for pipe sizes larger than 8" the detail does not show.

While in your viewport, your riser is visible while in the 2D Wireframe view.  However if you change the Visual Style to Conceptual or Shades of Grey/Shades of Gray, your 3D riser disappears.  You may notice if re-appears if you zoom out.

After printing your data in HydraLIST, when HydraVIEW opens you attempt to change the default printer. 

You get an error "Page Setup - Unknown filetype found 'HLTF'"

When opening HydraCALC SIZER, you get the error;  Run-time error '53': File not found

1)This error usually means that the user does not have full access for the folder. Or a lock file already exists and can not be delete. 2) real time virus scan blocking file. 3050

When drawing objects, you get these icons/images/boxes next to the drawn object.  If you hover over it, it mentions an osnap option

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Step 1a.1 - Error box - missing Pipe Type pointing to Ref 1 & Ref 2

can also be Step 1a.4

Revit could not complete the external command... Revit encountered a Attempt to modify the model outside of transaction

When closing a drawing in 3D, and later re-opening and returning to 2D, some of the drawing symbols show up looking like outlines (Hangers, Sprinklers, etc)