Woodland mansions will not generate when biome size is changed (anything different than 4). I tried it with customized wold on and biome size 3 - failed to generate mansion, biome size 5 - failed to generate mansion, biome size 4 -no problems.

It's not that the mansion should be in a specific spot but just not generate. There are no woodland explorer maps from villagers and the /locate command produces an extremely large lag and the message: "Unable to locate any Mansion feature". I tried the command even 300000 blocks apart in every direction. There are no mansions.

Video demonstrating the issue