Back in the 80's I once got a call to a hard drive on a Jaquard system giving read errors, also at an insurance company. Think the drive was a Trident one if I remember correctly of the old large removable disk pack type. Testing showed the head carriage would not seek beyond a certain cylinder for some reason. After stripping s few things away and delving into the mechanics of the head carriage I discovered a broken up Bic biro lying in the bottom of the head carriage guide assembley. It had fallen out from behind the operators ear she recalled while she was changing disk packs !