Slitherine

Multiple palaces being built?

are you sure they are not disbanded? You can sometimes get this if a region has been the the capital and lost/regained or becomes the capital of a new faction.

There is a routine to clear them up - you'll see the message about the locals disbanding the building for the infrastructure but it might take a few turns for that to fire.

This is rare but I have noticed this several times e.g. in Emporium, Emporia with 3x Epiteichismata.

EDIT: even in this game I have it: https://i.ibb.co/ZMskgZM/Screen-00000012.jpg

There can be multiple Abandoned Palaces in a region if it gets made a capitol and then conquered multiple times. Massilia/Emporia having multiples of Epiteichismata and their other faction-specific building per region is working as designed, that's a faction-specific mechanic for them.

Correct, that's a feature not a bug! A few rare buildings can be present several time. As for the abandoned Palace, the extra numerate should be removed the turn after, if not please send the saved game to support@slitherine.co.uk, reference this thread and say that's for Pocus, thanks.