The old world doesnt save at all, takes abnormally long too save, says its saved but nothing or is unable too save when windows gets out of sleep mode/idle/minimization these things have actually happened too me about 4 times requiring me too alt-f4 the game too get out of the softlock its stuck in  (this is the same world I have bug that the bug MCPE-42058 exists in so it may be correlated)