My GUI draws thousands of images using blit. This slows it down a lot. I tried copying  the code from  the innerBlit method, and calling the BufferBuilder.end method after all vertices have been created. It does  not work.

This is called for each image i want to draw:

builder.begin(Mode.QUADS, DefaultVertexFormat.POSITION_TEX);
builder.vertex(mat, X1, Y2, 0.0F).uv(0.0F, height).endVertex();
builder.vertex(mat, X2, Y2, 0.0F).uv(width, height).endVertex();
builder.vertex(mat, X2, Y1, 0.0F).uv(width, 0.0F).endVertex();
builder.vertex(mat, X1, Y1, 0.0F).uv(0.0F, 0.0F).endVertex();
builder.end();

and after the loop, this is called:

BufferUploader.end(builder);

I am also getting warning about byte mismatches.

How can I solve this?

Any ideas?