Your system testing found that the vertical voltage very close to the polarity switch point and within the 10% variance. This could continue to be an ongoing problem with any LNBF.
Both ports were originally reported to be working properly if used one port at a time (one STB connected at a time). The previous comments and testing did not involve the meter. The meter could have been initially used to test. Sorry did not know you had one. The original problem could have been a factory defect, but also could be related to interaction between STBs.
In the meantime, an electrical event took out the fusible link to one polarity probe. Was this an act of nature or ??? This may have caused additional problems.
Now testing indicates that the second port is outputting only horizontal polarity with only one port connected. This is a new problem.
Seems to be a moving target.... I can't force you to send it in...
The offer to test and replace remains on the table from post #25.
Titanium Dual LNB Problems :(