Slitherine

Hi. In every campaign starting in 1054 Zagwe capital is in Lalibela region on the first turn but in the second turn switches to Aksum region (the palace in Lalibela disappears and appears a new one in Aksum).

Did the new capital produce more auth than the old one before the move?

The new capital produces less authority (1.5) because the new palace there is a modest palace (the disappeared palace in Lalibela was a normal one (2.0). More downgrades happens in Lalibela because the rustic fort (0.1) is transformed into a rudimentary fort. There is no new fort in Aksum.
I have verified that this occurs in Zagwe both when played by me and by the AI.

Making further checks throughout the region I have observed that of the other two nations with more than one region, Alodia also undergoes a capital change (from Soba to Nuba) while Makuria keeps it in Dongola.
Furthermore, all palaces in all nations except Dahlak are degraded to modest palaces, and all rustic forts except Simien's are degraded to rudimentary forts.

All this happens at the start of turn two.

You're right, and the fixes will be included in the next patch. African nations will start with the Modest Palace and Drystone Masonry Fort. Thanks for your bug report!