If a person finds that his parshat or tefillin were not kosher to begin with even after a number of reliable and respected sofrim checked them and you were assured that the parshiyot and or tefillin were kosher to be used with a bracha. You then used these tefillin for a number of years. Can the sofrim or magia or person who sold these tefillin to you be sued in BAIS DIN not only for them not being kosher but for loss of mitzvah and BRACHOT LEVATOLAH? WHAT ABOUT MEZUZOT as well? This a very important question.
You cannot sue a person for the berachos levatalah that you have made. Although unfortunate of course, he will bear responsibility for this in the Court of Heaven, and not in the courts of Beis Din.
However, you can claim that the original purchase, or the services that you ordered from the relevant people, were a “mekach ta’us” – you wanted kosher Tefillin, and received non-kosher Tefillin. This will entitle you to your money back, and for this purpose you can take them to Beis Din.
Best wishes and hope that the next Tefillin will be better.