The bug
It appears net.minecraft.client.gui.font.providers.TrueTypeGlyphProviderBuilder.create(ResourceManager) (Mojang name) leaks the buffer allocated by com.mojang.blaze3d.platform.TextureUtil.readResource(InputStream).
It appears net.minecraft.client.gui.font.providers.TrueTypeGlyphProviderBuilder.create(ResourceManager) (Mojang name) leaks the buffer allocated by com.mojang.blaze3d.platform.TextureUtil.readResource(InputStream).
Looks like this was fixed in 1.15.2-pre1.