Problem description

An issue has been identified when running a PLAXIS 2D Dynamics calculation that includes horizontal interface elements at the model’s top boundary (YMax) while free-field conditions are applied to the model boundaries. This problem occurs specifically in version PLAXIS 2D 2025.1.0.1991.

During the calculation, a red cross icon appears, and the Log info displays:

Unknown error. [Error code: 604] 

You can view the Log info by double-clicking on the phase or by selecting View Phases in the Phases Explorer, as shown below:

To confirm your PLAXIS version and build, go to Help > About in the application menu.

 

Workaround

This issue is now resolved with the release of PLAXIS 2D 2025.1.2. Download the latest PLAXIS version here.

The issue occurs because PLAXIS 2D incorrectly considers the top horizontal interface as a potential free-field boundary, which leads to an error in version 25.1.0.

A simple workaround is to add a small dummy soil block above the top boundary of the model. This prevents the top horizontal interface from being picked as a free-field boundary. The dummy block (e.g. linear elastic material) can be deactivated so it does not affect the analysis.

If your project was converted from an older version, you can still open the original (pre-conversion) file using the relevant previous version. 
Side-by-side installation of the previous and latest PLAXIS 2025.1 versions is supported. 

This issue is now resolved with the release of PLAXIS 2D 2025.1.2. Download the latest PLAXIS version here.