Garmin 196 land mode problem

I have a Garmin 196 that I use primarily for flying, but also bought
the "automobile option" package that included the bean bag mount and
CDROM with road maps. When used in LAND mode, it works OK most of the
time, but sometimes gives crazy routing. Usually, it's right after I
deviate from the route it wants me to take (when I know a better route
than it does). It keeps trying to take me back to its original route,
long after that is less efficient than figuring a new route. The extra
time for its rerouting can get to 15 minutes before it realizes that
there's a better route (mine), when the ETA finally drops back to where
it should be.

Last week I had a much more serious problem, also in LAND mode, and
also after deviating from its initial route. I was going from
Morristown, NJ to Yorktown Hts, NY and, since I knew the route pretty
well by heart, had the unit on only to tell me distances to next exits
etc.. Its initial route was different from mine, but I figured that it
would eventually give up on tryng to get me back to its plan. But it
never did. When I was 15 minutes from my goal, it was telling me the
ETA was 45 minutes away! Even when I got to my goal, it was telling me
it was about half an hour away. I didn't have time to check the details
of its route that was going to waste a half hour getting me to where I
already was (within a tenth of a mile), but did check to make sure that
the goal's coordinates weren't somehow in error. I did this by saying
"direct to" and hitting ENTER. That directs you to the same goal as
last time. When I did this, it told me my ETA was 1 minute later or
thereabouts, not half an hour. So the goal's coordinates were not in
error.

Has anyone else seen similar behavior and, even better, does anyone
have a fix?

The LAND mode is also poor in that it seems to assume you will travel
at the speed limit, with no regard for traffic lights and stop signs.
This came in while I was in Manhattan, travelling from Riverside Drive
and 115 St going north toward the George Washington Bridge. I knew
Riverside Drive was a better way to go than Broadway (which the 196
told me to take) since Riverside Drive has few lights, whereas Broadway
has many. I doubt there's a fix for this other than for Garmin or the
map provider to get smart.