I don't know if anything has changed since then, what you say was in 2024, I saw 2 of the problems you talked about, but the problem of downloading files and the download stopping, I found a solution, that the cids change in versions, According to IPIP-499, the same cids are now obtained for different versions and different devices.

the export and import of car files is something very recent that was added in version 0.42, in previous versions I saw that the file you uploaded could not be downloaded, but now with this you can make backup copies of what you had in your node in case they are lost, I don't know if that was the problem you went through at that time.

although with DHT I still haven't noticed the problems you talked about.