I have a 2009 volvo V50 that acts up ever so often . It shifts perfect always. When taking extended trips maybe more than 30 minutes (no true consistency) the "urgent transmission light comes on" when slowing to pull over it makes a hard downshift.
Turn car off and do a reset and light goes off and you can continue driving. It may not do it for a week or more and then this scenario repeats. I did attempt one time to get back on highway and continue highway speed and the issue reoccur not very far down road. I have learned if I lower my speed and or RPM (take backroads rather than highway) it seems to avoid the light coming on. When this happens I do smell transmission fluid but only when this is triggered. There is no possible way to take on long trip. Local Volvo specialist no help. They kept it for a week and drop around town but could find nothing wrong. They never took on extended road trip to duplicate the issue. It seems like a transmission temperature fault and may be related to transmission temp.. the only thing the local Volvo specialist did was change fluid and double le check fluid level.
volvo specialist said only remedy is replace transmission which seems crazy. Surely it is some sort of bad sensor of sorts.

 

The good news is that the transmission shifts correctly at least some of the time. That would indicate that the clutches are still working well. Generally, when you have an intermittent situation like this, the first thing to suspect would be the shift solenoids. The good news is that replacing them isn't too hard, or too expensive. IIRC, it cost me around $100 for the set, and took a few hours to swap out (including doing a video of the process, which is on youtube). The solenoids can get "gummy" and create situations where the valves are not in the right position for the conditions, which can cause funky shifting, lack of drive, etc.

And yeah, the dealer (and probably a lot of shops) don't want to be bothered trying to fix a transmission when they can make SO much money selling you a new tranny. The dealer wanted $6K from my V50's previous owner for a new tranny, which I fixed as described above.