We have found that when doing a heads filling calibration there are extra steps that should be taken to ensure an accurate calibration. Manually changing the liquid level sensors back to factory values will help the machine calibrate the sensors accurately. Do do this extra step simply enter maintenance mode then go under the Parameter Manager. Scroll down to Heads Filling. Then change the first four values to look like the values below.
Then follow the normal Heads filling calibration procedure. Here is a link to heads filling Blog link- https://www.cati.com/blog/2016/06/head-filling-error-and-calibration-your-objet-desktop-can-display-an-error-related-to-heads-filling-while-it-is-printing/