windowPositionAndSizeConfig.tag is only being saved or changed from inside a local singleplayer game on a proper game exit.
its not being saved or created
The file windowPositionAndSizeConfig.tag seems to corrupt sporadically, causing the game to completely fail to start, until the file is either erased or the default world's name is changed(the file seems to store the data on a per-world basis, so changing the world's name will either point to an uncorrupted section of the file, or cause a new section to be generated with default values).
What causes the file to be corrupted is unknown though, and feedback regarding that is appreciated.
The stacktrace of the Exception resulting from a corrupted windowPositionAndSizeConfig.tag file is:
0.1932 java.lang.NullPointerException ^ at obfuscated.asA.a(SourceFile:114) ^ at obfuscated.asA.h(SourceFile:105) ^ at org.schema.game.common.Starter.main(SourceFile:874)
'^' indicates, that this row is a continuation of the row above.