The jigsaw block in the entrance_path_5 structure in ancient cities that presumably is supposed to be named minecraft:entrance_middle is blank, so the piece can never be generated.
Steps to reproduce:
Look at any number of ancient cities
Results:
entrance_path_5 never generates
Expected results:
entrance_path_5 generates sometimes
I can also confirm this behavior.
[media][media][media]Here are some more reliable steps on how you can go about reproducing this issue.
Steps to Reproduce:
Summon the "entrance_path_5" structure by running the following command and powering the structure block.
Locate the affected jigsaw block which can be found towards the east of the structure.
Open the jigsaw block and look at its contents.
Take note as to whether or not the jigsaw block is blank.