MS3 concentration reading problems

These past few months, seemingly randomly, my samples would show an unusually high concentration (>90%) when I preview the sample. The concentration readings remain the same no matter how much I dilute it.

It should be mentioned in the plot that is displayed below the concentration bar shows a linear plot, as opposed to various peaks that normally occurs when concentration readings are working in.

The only troubleshooting I've been able to do is uninstall the aperture tube, install a DIFFERENT aperture tube only to uninstall it and reinstall the initial aperture tube. It is a redundant process.

The service at Beckman Coulter have not been unenthusiastic as we do not have warranty on the instrument. In fact, a tech came in to replace the expensive motherboard, which was initially perceived as the problem, only to have the problem persist.

Any recommendations or thoughts would be appreciated.