After setting up a fitting in the Parts Tree then trying to Insert Fitting, you get the Unhandled Exception error below

eLockViolation

After creating a legend for your 3D riser, you use the ILT command to insert a legend tag.  It inserts the tag, but you get the error.  You have to click CONTINUE then repeat the command to place another one.

Unhandled exception has occurred in a component in your application

Arithmetic operation resulted in an overflow

Application does not support just-in-time (JIT)

After buiding your 3D risers, raising to 3D, exporting to a Persistent Model and Navisworks successfully, your 3D riser is missing, with the exception of the skipoles

Your layers are on and the 3D_DETAIL layer is present, unlocked, thawed and visible, you just can't see the pipe and fittings.  The one customer reporting this said they disappear if the drawing is closed then re-opened.  They'll be visible in viewports as well, just not in 2D view.

When attempting to Launch HydraLIST to start building your riser, you get this error;

When trying to insert a 3D fitting via the Fittings Parts Tree, the user gets the error message;

Microsoft .NET Framework
Unhandled Exception has occurred...
Argument 'Key' is not a valid value

When user clicks CONTINUE and tries to use the INSERT button to insert a fitting, another dialog box pops up

INSERT FITTINGS
Unhandled Exception...
Index was out of range.  Must be non-negative and less than the size of the collection.  Parameter name: index

Unknown *invalid_ skipole* 3D Risers HydraCAD v50