Why is it a problem with it not going to slide lock? If this is for USPSA, you really shouldn't ever get to there. If it's IDPA, I have no ideas on that as I've never shot it.
But, I find it's always easier to reload before slide lock.
What you are doing, though, is riding the slide lock with your thumb. I do this all the time with any pistol without a thumb safety for me to ride on. You can correct your grip, or just not worry about it.