Hello @Raphael Jöbges ,
Thanks for additional clarification regarding the issue.
Yes, if your missing column is complex type (Multiple choice type) then it is not supported by the ADF SP Online list connector which is why you are seeing this issue.
Please refer to below note from public doc:
Please feel free to log your feedback in IDEAS forum : https://feedback.azure.com/d365community/forum/1219ec2d-6c26-ec11-b6e6-000d3a4f032c.
All the feedback shared in this forum are actively monitored and reviewed by respective product owners. Also please do share the feedback link once it is posted so that we can share the info with respective product team for further review.
Hope this info helps.