banner map markers are not saved to maps created in 1.12

you can add a map marker to 1.12 created maps, but after “save and quit” and then reloading the world, the banner is gone. 

if you create a brand new map in the same world map markers are saved fine and reloaded fine.

reproduce:

open a 1.12 world in 1.13 that had a map created in 1.12

place a banner in the world

add the banner to the map created in 1.12

(you will see the banner on the map just fine at this point)

”save and quit”

reload that world

banner will no longer be on the map

this is a real pain to those of us that have mapped anlot or our world. we would have to create a new map and re-explore to use banners as markers