It is just mentioned in the crash-report
at com.lowdragmc.shimmer.client.shader.ReloadShaderManager.backupNewShaderInstance(ReloadShaderManager.java:114) ~[Shimmer-forge-1.20.1-0.2.4.jar%23427!/:?] {re:mixin,re:classloading}
The start or run bat file
There you will find the line
java @user_jvm_args.txt @libraries/net/minecraftforge/forge/1.18.2-40.2.18/win_args.txt
Change it to
"C:\Program Files\Java\jdk-17.0.9\bin\javaw.exe" @user_jvm_args.txt @libraries/net/minecraftforge/forge/1.18.2-40.2.18/win_args.txt
pause
Keep the quotation marks and make sure the path is correct
After installing Java 17, put the path into your script or remove Java 20
"C:\Program Files\Java\jdk-17.0.9\bin\javaw.exe" @user_jvm_args.txt @libraries/net/minecraftforge/forge/1.18.2-40.2.18/win_args.txt
pause