[MCL-16917] doesn't start on Debian 10 after the first time

Yesterday when I purchased & installed Minecraft.deb, it was able to run. However, when I run minecraft-launcher today this is all I get:

anna@e7240:~/Downloads$ minecraft-launcher
[0215/200724.384493:INFO:main_context.cpp(108)] CEF initialized successfully.

[0215/200724.384590:INFO:main_context.cpp(109)] CEF version: 3.3202.1694.gf061c23

[0215/200724.494605:ERROR:sandbox_linux.cc(346)] InitializeSandbox() called with multiple threads in process gpu-process.

In the background, this is running:

anna@e7240:~$ ps ax|grep mine
 5649 pts/1 Sl+ 0:00 minecraft-launcher
 5654 pts/1 S+ 0:00 /opt/minecraft-launcher/minecraft-launcher --type=zygote --no-sandbox --lang=en-US --log-file=/home/anna/.minecraft/launcher_cef_log.txt --launcherui
 5673 pts/1 Sl+ 0:00 /opt/minecraft-launcher/minecraft-launcher --type=gpu-process --no-sandbox --lang=en-US --log-file=/home/anna/.minecraft/launcher_cef_log.txt --launcherui --disable-accelerated-video-decode --gpu-vendor-id=0x8086 --gpu-device-id=0x0a16 --gpu-driver-vendor --gpu-driver-version --gpu-driver-date --lang=en-US --log-file=/home/anna/.minecraft/launcher_cef_log.txt --launcherui --service-request-channel-token=25E04E41BC895DB68D3E37ABD898898D
 5708 pts/0 S+ 0:00 grep mine

I had openjdk11 installed when it stopped working. I also tried installing openjdk8 based on some googling, but that didn't help:

anna@e7240:~$ dpkg -l |grep jdk
ii openjdk-11-jre:amd64 11.0.9.1+1-1~deb10u2 amd64 OpenJDK Java runtime, using Hotspot JIT
ii openjdk-11-jre-headless:amd64 11.0.9.1+1-1~deb10u2 amd64 OpenJDK Java runtime, using Hotspot JIT (headless)
ii openjdk-8-jdk:amd64 8u252-b09-1~deb9u1 amd64 OpenJDK Development Kit (JDK)
ii openjdk-8-jdk-headless:amd64 8u252-b09-1~deb9u1 amd64 OpenJDK Development Kit (JDK) (headless)
ii openjdk-8-jre:amd64 8u252-b09-1~deb9u1 amd64 OpenJDK Java runtime, using Hotspot JIT
ii openjdk-8-jre-headless:amd64 8u252-b09-1~deb9u1 amd64 OpenJDK Java runtime, using Hotspot JIT (headless)

I moved ~/.minecraft out of the way and now it launches, but I'm worried that it will happen again my kid will lose all the stuff he's built. I can still put the old .minecraft directory back, and minecraft-launcher will stop working.

Here's what I get with a working .minecraft directory, by the way, when I start it and then quit at the end:

anna@e7240:~$ minecraft-launcher 
[0215/202957.837488:INFO:main_context.cpp(108)] CEF initialized successfully.

[0215/202957.837611:INFO:main_context.cpp(109)] CEF version: 3.3202.1694.gf061c23

[0215/202957.946973:ERROR:sandbox_linux.cc(346)] InitializeSandbox() called with multiple threads in process gpu-process.
Segmentation fault
anna@e7240:~$