We have anecdotal evidence that this may be true. We are researching this further. We also have support tickets open with RWS, but we've made almost no progress in several weeks.

These imports end up being used to create very large publications, as well. We have trouble opening them even when increasing timeout settings. A baseline may have 15,000 objects and we see "spinning cursor" for many minutes at a time. Navigation and doing simple tasks in Publication Manager in these large publications are also very difficult and slow.

Before Content Importer, I believe you used to be able to configure a background task role for importing content (i.e. a "batch server"). Is this still possible?

Have we hit a scalability limitation? Is there a "maximum size" for publications?

Tridion Docs 14 SP3. Servers configured well above recommended CPU/RAM recommendations.