My first two thoughts would either be that the transmission fluid level is low and needs to be topped off, or that the transmission mode selector switch on the drivers side of the transmission is in need of cleaning or replacement.

The transmission fill plug/hole is on the passenger side of the transmission near the top and the fluid level should be about even with the bottom of the hole with the plug removed. Sadly, there is no transmission dipstick or dipstick tube through which to add fluid on the Vehicross, so if necessary, adding fluid has to be done through the actual fill/plug hole.

The contacts on the transmission mode selector switch (on the drivers' side of the transmission) sometimes get corroded, and that can cause erratic behavior from the transmission. Sometimes the switch can be removed, cleaned, then reused, and sometimes just replacing the switch is necessary. Some here have also stated that when that selector switch was the problem , they'd also noticed that the dashboard lights that indicate what gear the transmission is in also behaved erratically, so if you've noticed that too, the mode selector switch is likely the culprit.

Mode selector switch http://www.vehicross.info/gallery/sh...hp?photo=15781

Hope this helps and that it's something relatively simple like one of the two things I've described.

Welcome to the site Vincent.