Mitsubishi Repair: Lancer transmission, magic performance, mitsubishi lancer

Question
Hi, my name is Kristjansson and I have a ´98 Mitsubishi Lancer 1600cc GLXi 1600cc which has a faulty automatic transmission.
When I´m driving, it sometimes doesn´t shift up from the first step("gear") until around 4500-5000 rpm, and then is like it skips the second steps and goes straight to the third step. This happens almost every day.
And there is another problem, sometimes it is like the transmission drops out of gear somehow and goes to nutral for a bit, and then it roughly jumps to first or second step maybe one-two times in a row, and then drives normally.

I took the car to a local mitsubishi workshop(but dont have much faith in them) and they didn´t find the problem, just said that the transmission was probably just about to brake and that I needed to find another one. I´ve driven few thousand kilometers since..

A mechanic I asked about this problem told me to try adding something called "Lubegard platinum" to the transmission fluid, but I really dont believe in these magic-performance-liquids.

What do you think is wrong with my transmission?
Thanks,
Kristjansson. (Excuse the bad english, I´m from Iceland.)

Answer
Kristjansson,
I would agree that simply using a different transmission fluid will not fix your problem.  Your issue may be caused by a malfunctioning solenoid and is not engaging the proper gear.  This can also be caused by a faulty transmission computer.  A bad computer can exhibit many different shifting problems and are not always easy to detect.  You may have better luck seeking out help from a dealership mechanic or a transmission shop where the mechanics are familiar with your particular transmission.
Good luck!