I assume that as part of your preflight you switched to PLN and looked at your LEGS page in your MCU and used the STEP button (lower right LSK) and did not see any discos when you went through step by step?

It is not unusual to have weird double-backs and strange excursions, usually because I put in the wrong waypoint, or there were duplications or whatever.  You catch those before you take off  ;)  That's what I mean by saying you have to monkey with them until they're right sometimes.

I think a lot of simmers (not  you) expect too much from certain equipment.  There is no magic button.  A good example is descent.  VNAV is not your magic "take me home" button.  Once you learn how the different ways you can descend work, and what they're each good for, then you can use them sensibly.  Now tonight, I do plan to use VNAV, because I'm not fooling with ATC and just want to see what the airplane can do for me.

Anyway, if you had no discos when you left, I don't see how you could suddenly develop one in flight.  (Unless you used your awesome new DEL powers for evil.)  If that happened to me, I would just click on the waypoint I was supposed to be going to on my LEGS page, so it showed up in the scratch pad, then hit the top left LSK to go direct.  No big deal as far as that goes, but you're flying with something wonky.

For how little the AIRAC cycles cost, and since you can use them in any airplane you have that Navigraph supports (not the same one, but you can download installers for each for just the one price) I would indeed recommend it.  I really don't know what the 757 Captain ships with, but I would guess the last free one, which is pretty out of date.  Plus, you get a lot of procedures, too, that are pretty reliable.  You buy "credits" at Navigraph that you can use to buy your AIRAC cycles, and also procedure charts and even en route charts if you want to, but that costs more.  While a lot is available online, there's something to be said for having what you want when you want it, too.

Maybe Navigraph is why I'm enjoying so much success, I don't know.

Hang in there.  This is not easy stuff at the beginning.  Once you start understanding exactly why things work, it will click for you.  Just to make sure about the RTE page, although I used one airway and "exit" a real plan will probably have more, though, and those all have to get entered.  You probably know that, but thought I'd mention it.

The STAR I wanted to use tonight was at AirNav, but not in my FMC database.  It happens.  So I just kind of made my own by combining a STAR I did have with the approach plate for the runway I intend to land on, so I basically wind up at the initial approach fix at the right speed and altitude.

By the way, I cranked up traffic at KMIA and was no. seven for takeoff with other planes landing, in front and behind me.  I was getting 20 FPS in spot, 17 looking out the vc window, and 15 on spot during climbout looking at the airport behind me.  In cruise I'm getting 25 from the vc and 30+ in spot.

With the sunlight putting all the knobs in the vc in bright relief, and the Atlantic Ocean glistening out the window, it is really a beautiful trip.