Some heads get corrupted (and corrupt the chunk they are in) during the upgrade from 1.13.2 -> 1.14

After upgrading an existing world from 1.13.2 to 1.14, my server crashes whenever someone enters a region with heads. This is random, but I assume some heads (skulls) get corrupted during the conversion process, and whenever someone loads a chunk in which there is a corrupted skull, the server crashes.
I am using Spigot, however this also happens using the Vanilla server.
The world conversion was done via the single player worlds (loading the 1.13.2 world and letting it be converted to 1.14).