Z-axis leadscrew/bearing moves up under cutting load 🇬🇧

Hi,

I recently bought a used Tops CNC V1 and noticed a problem with the Z-axis.

When the face mill applies pressure to the workpiece, the entire Z-axis moves upward. The leadscrew together with the lower bearing gets pushed out of the lower plastic mount.

I attached two pictures showing the issue.

Has anyone experienced this before or knows what could cause it?

Any help is greatly appreciated. Thanks!