As many have noted, a common failure mode in the LNC2
is the flap's (electromechanical) relay wiring and contacts.
Has anyone replaced their flap control relays with
solid-state controls? I would expect a considerable
increase in reliability if properly designed.

Taking that idea a step further, the limit switches
could be made latching so that coasting past the
switch would no longer be a problem. i.e. when
the controller detects that the down limit switch
is triggered, it shorts the motor until it detects
the up control switch is closed.

Has anyone done this already?
Or should I go ahead and design it?

Bob,

 

The limit switches detect the presence or absence of the stabilizing rod.  They are self-latching for any flap motor position at or beyond their limit.

 

The relays work just fine for most everyone.

 

However,  Solid state like this: