(This post is cross-posted from SuperUser)
Up until recently, Minecraft has been acting really laggy in a sense that it will fill up the RAM and VRAM until everything in the system starts becoming unresponsive. However, this only happens when Minecraft is in full screen and when I switch to another window. When it is in windowed mode, it doesn't cause the problem.
I have tried multiple things such as updating and downgrading NVIDIA GPU drivers, switching Java versions, adjusting memory allocation from 2410 MB to 512 MB, and even resetting the launcher, but all of those mentioned did nothing to solve the problem.
Also, as pictured below, there is no way Minecraft would fill up that much RAM, VRAM, and GPU usage, because it is working normally before, and the VRAM usage is kept to about 0.3 GB.
Oddly enough, this doesn't seem to happen in other Minecraft versions. I have tried playing in OptiFine 1.14.4 and OptiFine 1.17.1 and it is working perfectly fine. I even tried reinstalling OptiFine 1.12.2, but it didn't work.
UPDATE #1:
I have also tried playing in Forge 1.12.2, ForgeOptifine 1.12.2, and even Release 1.12.2, and they all have the same problem.
I have also tried repairing Java through the installer (I'm using Java 8 OpenJ9), and I thought it solved the problem for Release 1.12.2, but when I switched back to OptiFine 1.12.2, the problem persists.
Also, I have looked at the logs and it was flooded by this:
[15:30:45] [Client thread/FATAL] [net.minecraft.client.Minecraft]: Error executing task
java.util.concurrent.ExecutionException: java.lang.NullPointerException
at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[?:1.8.0_292]
at java.util.concurrent.FutureTask.get(FutureTask.java:192) ~[?:1.8.0_292]
at net.minecraft.util.Util.func_181617_a(SourceFile:47) [h.class:?]
at net.minecraft.client.Minecraft.func_71411_J(Minecraft.java:1088) [bib.class:?]
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:398) [bib.class:?]
at net.minecraft.client.main.Main.main(SourceFile:123) [Main.class:?]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_292]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_292]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_292]
at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_292]
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135) [launchwrapper-1.12.jar:?]
at net.minecraft.launchwrapper.Launch.main(Launch.java:28) [launchwrapper-1.12.jar:?]
Caused by: java.lang.NullPointerException
at net.minecraft.scoreboard.Scoreboard.func_96511_d(SourceFile:228) ~[bhk.class:?]
at net.minecraft.client.network.NetHandlerPlayClient.func_147247_a(NetHandlerPlayClient.java:2034) ~[brz.class:?]
at net.minecraft.network.play.server.SPacketTeams.func_148833_a(SourceFile:117) ~[kl.class:?]
at net.minecraft.network.play.server.SPacketTeams.func_148833_a(SourceFile:13) ~[kl.class:?]
at net.minecraft.network.PacketThreadUtil$1.run(SourceFile:13) ~[hv$1.class:?]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[?:1.8.0_292]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[?:1.8.0_292]
at net.minecraft.util.Util.func_181617_a(SourceFile:46) ~[h.class:?]
... 9 more
Also this one:
[15:35:49] [Client thread/ERROR] [net.minecraft.client.network.NetHandlerPlayClient]: Received invalid update packet for null tile entity at BlockPos{x=186, y=104, z=115} with data: {x:186,Text4:"{\"text\":\"\"}",y:104,Text3:"{\"text\":\"\"}",z:115,Text2:"{\"text\":\"\"}",id:"minecraft:sign",Text1:"{\"text\":\"\"}"}
