This caused me to lose 234 Minecraft days of a survival. If you lock your PC while your world is loading, Minecraft crashes and your save file is corrupted. My PC locks after 15 minutes when I log in, unless I lock it manually. I miss my world and found many bugs in it.
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What OS do you use? Any parental control software or similar that might interfere?
Also, please attach the crash report found in [minecraft/crash-reports/crash-<DATE>-client.txt|https://minecrafthopper.net/help/finding-minecraft-data-folder/]
here.
If you cannot find a crash report, please attach the full launcher log found in [minecraft/launcher_log.txt|https://minecrafthopper.net/help/guides/getting-minecraft-logs/]
.
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I have a 64 bit OS, and my account is monitored by my parents using Windows Family. I found no crash report and launcherlog.txt is too big to fit in one comment. I also don't know how to attach files to a comment.

Also, I think this bug has existed since the loading screen changed from a percentage to that square the fills up with white, green, and blue pixels.

Is this somehow connected with MC-115237?

I feel like it probably is, but from my testing, it only happens if the "Pause on lost focus" setting is on.

It's a frame perfect bug.

Can this issue still happen in 1.19.4?