I think the problem comes from using mods. You can actually patch UP3 to 4.11 and in the selector chose 'stock game' to run 4.11 and Ultrapack for UP3 (jmg-thing also needs switching), however if you setup a mission in QMB on UP3 with modded planes and then switch to stock, the game will freeze as it reads the last.quick from UP3. Thus a void file as a hotfix is not necessary. People who experience the freeze either are using 4.11 and UP3 on the same install, or use the configuration files which previously were used for UP3.
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