I created a world to use with 1.14 snapshots. I entered the End and beat the dragon while the end gateway portal bug was active. When the end gateway portal bug was fixed, I used end crystals to spawn a second dragon. The game generated a new set of towers and also modified (and corrupted) the original set of towers. See attached screenshot.
Environment
Windows 7, bundled Java with arguments: -Xmx5G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=16M
This was caused by a bug in the earlier snapshots (MC-138448).