Volvo 440 2.0i Automatic transmission problems

I have a 440 2.0i from 1997 which only did about 30.000 miles.
From one day to another the automatic transmission did not work correctly anymore. Sometimes it seems to skip the 2nd gear, jumping to third which causes the engine to overdrive and nearly stall.
This does not happen all the time though. I currently drive around changing gears from 1,2 and usually 3. I don't use Drive anymore as that does not work.
Kickdown still works OK.
The volvo dealer said they THINK it MAY be the transmission that needs replacing but that is so expensive.
I had the oil changed in the transmission but that did not help.
When slowing down I can feel the engine changing gear so how
can the transmission be broken if it is working correctly sometimes?
ANYBODY, PLEASE HELP !!!
Could it be an electronic problem ?
If so, how can it be solved?
Could it be that because I only drive around locally (in town) that
this has happened?

I went to a specialist and he told me that the regulator had some broken items. Not expensive to fix, however, the whole gearbox needs to come out in order to get to it, which is expensive!