Trying the DDL command gives the error; 

Usage: (acad_strlsort <list of strings>)

Error bad argument type: consp nil

When raising to 3D, you get the error message, "Error loading the Error GUI has occurred.  How ironic."

The drawing will raise to 3D, but you won't see the error dialog window.

Trying the Show Model Errors command (SME) produces the same error

When the OK button is clicked from the AutoLIST Setup window, it'll either hang/freeze or crash with a Fatal Error

Unhandled e0434352h Exception at 25CE17Ah

When raising to 3D, the drawing hangs.  On the progress bar at the bottom, it may be stuck at, "Creating entry for mains database"

If you turn off the Show Fittings in Model option found in the 3D Modeling Settings window (3MO command), it likely will create a model.

The only option is to End Task AutoCAD to stop the process.

When setting up a new head, the dialog that displays the head symbols to be selected appears, is empty, and then drawing crashes,

When attempting to open HydraCALC Sizer, you get this error;

Error:260:0:0

"Well this is new, not sure what's happening with your hardware lock, please get a current 'fix file' from Hydratec"

Error occurs when using some commands.

Autodesk has just released AutoCAD 2026.1.2 - and it breaks HydraCAD. It includes a major programming change by Autodesk that will require a lot of work and a large update by us. That update is being worked on right now, along with a version of HydraCAD for AutoCAD 2027. Both are now affected by essentially the same programming change.

BinaryFormatter serialization and deserialization are disabled within this application. See  https://aka.ms/binaryformatter for more information.

Other commands with this error;

Sprinkler Layout dialog (SL command)

When viewing a plot, hydraulic reference points in the HYD2 layer have thick text.  Editing lineweights for the layer does not make a difference.

Error occurs when tying to select any option in the Hangers button

Using negative floor elevations and drop windows with specified lengths, drops give a warning that takeout was greater than it's length, when going to 3D.

Error Finding Hanger Information when generating 3D Hangers

Revit could not complete the external command... Family symbol is not valid for this instance

When trying to place a hanger you get this warning.

"There are identical instances in the same place. This will result in double counting in schedules."

HydraCAD for AutoCAD drawing models imported into AutoCAD or Navis do not show Properties for our custom objects: HydraPIPEs, HydraHEADs and HydraFittings on machines without our software.

Launching AutoCAD causes a hard system crash as it loads some HydraCAD plugins, the last one seen is HCADMainBase.arx. The machine crashes every time — it does not reach the AutoCAD interface. When HydraCAD is uninstalled, AutoCAD launches and runs normally with no crashes.

Opening AutoCAD/Revit/Navis gives Device limit reached message after opening a drawing or model.

Opening AutoCAD/Revit/Navis gives Device limit reached message after opening a drawing or model.

When placing clevis hangers or adjustable ring hangers on a 10-inch pipe drawing in Revit, the hangers render incorrectly with missing 5/8 rods.

When trying to add reference points, none are added and this error shows:

After inserting a valve, it does not appear in the 3D view. There is blank space where the valves should be.