"The problem seems to be that existing nether fortress bounding boxes have disappeared, causing normal nether mobs to spawn rather than nether fortress ones.[..]Newly generated fortresses are unaffected and behave as expected."
yes to fix this you could use a program like mcedit or chunky to delete the chunks you havent build anything on. and save the world. then you could copy paste the content into you save file in DIM-1. thats the content of the nether. if you join again mc reloads the nether. your structures you didnt delete will be there. for instance your base. the mobs will spawn again in the fortress. (for me enderman didnt spawn too. and now they do)
for wither skeletons farms i would recommend structure block to save the structure before deleting. Or using mcedit and copy pasting the structure later again. that should some how work. this way a year ago i relocated my whole base (a castle town) with about 10+ chunks... because of a bug like this when switching to new version my whole world got corrupted. the world looked totally different then shown on mineatlas for instance. and i wanted to relocate to get the new 1.13 features... so this works 100%. i tested...
Peter Schneider
"The problem seems to be that existing nether fortress bounding boxes have disappeared, causing normal nether mobs to spawn rather than nether fortress ones.[..]Newly generated fortresses are unaffected and behave as expected."
yes to fix this you could use a program like mcedit or chunky to delete the chunks you havent build anything on. and save the world. then you could copy paste the content into you save file in DIM-1. thats the content of the nether. if you join again mc reloads the nether. your structures you didnt delete will be there. for instance your base. the mobs will spawn again in the fortress. (for me enderman didnt spawn too. and now they do)
for wither skeletons farms i would recommend structure block to save the structure before deleting. Or using mcedit and copy pasting the structure later again. that should some how work. this way a year ago i relocated my whole base (a castle town) with about 10+ chunks... because of a bug like this when switching to new version my whole world got corrupted. the world looked totally different then shown on mineatlas for instance. and i wanted to relocate to get the new 1.13 features... so this works 100%. i tested...