Matiz automatic transmission issue

Greetings. The symptoms you describe could stem from several factors. Have you checked the transmission fluid level recently? Low fluid can definitely cause slipping and erratic shifting. Also, when was the last time the transmission fluid was changed? Over time, the fluid degrades and loses its ability to properly lubricate and transmit hydraulic pressure. Finally, any recent work done on the car that might have impacted the electrical system?

Thanks for the quick reply! I haven't checked the transmission fluid level myself, to be honest. I'm not really sure how to do that on an automatic. Also, I'm not sure when the fluid was last changed. I've only had the car for a couple of years. Regarding electrical work, the battery was replaced about six months ago, but no other electrical work has been done. Is there anything else I should look at, or should I take it in somewhere?

Given your unfamiliarity with checking the transmission fluid and the fact that the battery was recently replaced, it would be prudent to have a qualified technician diagnose the issue. The undervoltage condition from the battery replacement may have affected the transmission control unit or related sensors, contributing to the symptoms you've observed. Continuing to operate the vehicle in its current state could potentially exacerbate the problem and lead to more extensive damage. A professional diagnosis will pinpoint the root cause and allow for appropriate repairs, such as an oil replacement costing 240€.

Thanks so much for the advice! I took it to a mechanic, and it turned out that, just like you suspected, the transmission oil needed replacing and there was some undervoltage issue. They replaced the oil, and everything seems to be running smoothly now. I really appreciate your help!