Take it off spot focus when you're not shooting through things like branches and such. If you set it to spot, when you're that close and get in on the eye, spot focus may not have enough contrast to grab focus and will continue to hunt a bit.
Turn off IS (OS, in this case, I think)
Make sure you're outside of the MFD of the lens; lenses like that, even in "macro" mode do not focus as close as a true macro lens would and it appears you could be right on the verge.
If you must touch the camera without using a release, be certain to use a 2-s timer at minimum. Depending on how resistant your tripod is to vibration, you may need to go to the 10s timer to give the unit time to balance out.
You can check this for yourself by going into Live View, go to 10x magnification and then do a half-press of the shutter to focus while on the tripod. Then, watch the LV screen when you let go of the camera and see how long it shakes after you let go.