It's an old post, but today but it was the only one I found mentioning HOLD issues. This old problem is not happening to me anymore, but today, while trying to do a holding, despite setting heading 27X it was going to 25X. It circled properly but when I tried to leave the HOLD pressing EXIT button, the whole FMC froze. I could control the plane but only altitude was moving, despite the wrong value.
I used to hate this plane when I bought it, but after a few updates I tried it again and I'm loving. I hope you guys keep fixing this issues.