Posted for "colyncase on earthlink" <colyncase@earthlink.net>:

 just a data point.   I had an stec-55x in my c172rg.
 It took over a year to get the installation to work properly.
 All sorts of failure modes: uncommanded turns, going offline,
 failure to lock on etc.   We replaced lots of stuff.
 
 In the end it ALL came down to the silly connector they put on the back of
 the tray.
 Replacing the connector and all the pins and the connector housing solved
 the problem, but that might have been overkill.
 It turns out the connector housing is plastic and is held on by two bolts
 that go into the back of the tray.  Every time you take out the computer and
 put it back in again, you are wearing out those through holes in the plastic
 housing.
 
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