Unwanted Hydraulic Head BCs created during simulation

Dear all,
recently I have run into a problem I cannot figure out. When running a simulation, I find many randomly scattered hydraulic head boundary nodes in the .dac file that are not present in the .fem file before simulation and not wanted either. I also believe these nodes massively distort the simulation results.

The model is a 2D, fully saturated model with automatic timestepping. I have some fluid-flux boundary conditions defined but no hydraulic head boundaries. There is a time-dependent source/sink term that changes every month and I have a parameter association link for the hydraulic head to define the initial hydraulic head in the model at the beginning of the simulation (see attachments). Could this be the problem? Other than that everything is pretty standard and I have no idea where these unintended hydraulic head boundary nodes could come from. Tested several times now, similar result every time.

Attachments show the hydraulic head parameter association link and the hydraulic head boundary nodes after simulation.

I'd be thankful for any hints or ideas!

Thanks,
Lennart

This looks a bit like BCs created on the basis of a top or bottom constraint on hydraulic head (defined in the free surface settings). This, however, I'd not expect in a fully confined model... Could you check whether it's really confined?

This was indeed the problem, the model was top-constrained for some reason. However, problem solved. Thank you very much!

You're welcome!