general problems of the 1997 Mercury Grand Marquis

I have 3 Mercury Grand Marquis, 1997, 1996, & 1992. Within the last 14 months, 5 of the 12 window regulators have failed. All vehicles have been garage kept for the most. No unusual or excessive usage to any of these windows. 1992-has ~162k miles-had 2 window regulators fail-driver & front passenger side 1996-has ~33k miles-had 1 window regulator fail-driver door 1997-has ~62k miles-had 2 window regulators fail-driver door & rear driver side two of these windows (1997) have been repaired by a local Ford dealer at approx $190. 00 each. This is a very poor record (42% failure rate) for these parts and I believe there must be a manufacturing defect and some mediation should be considered.