TWO SYMPTOMS:

Drawing fittings and pipe look disjointed, like that time an alien team of scientists were performing out-of-phase medical experiments on the Voyager crew.

Or, on the way into Revit, you get this error;

Error (must be addressed in order to continue)

Revit has experienced an unexpected error.  The operation has been cancelled to protect your project from corruption

Deleted element

When reporting the error, you may see this;

Hashtable head_table, Hashtable FLXpipeTable, List '1 listFtgs, flexpipes PipeTypeInfo ptInfo

1. mismatched files HCADexports.dll and HcadAquaFlex_50_1.arx Unhandled Exception Make Revit Content HCAD Revit 4.0.0.3

While importing an AutoCAD model into Revit, you get errors listed below;

Sprinkler heads were not properly defined with a part number within the HydraCAD drawing. Therefore, Revit used a default sprinkler head symbol which happened to be a pendent sprinkler symbol. Revit

Missing commands on Add in for HydraCAD when trying to generate a RevitLink conversion

AutoCAD entities too far out in space for revit to handle

1. dry pendent sprinkler is defined in the drawing and cannot be generated as Revit content Retrieve content Revit revit Link 4-2

Unknown, but likely that creation of Revit content will still be accomplished.

Revit Link was not installed with Admin Rights