Tabbing through Cells when protected doesn't work

[LRay67]

I have a worksheet that has clickboxes and the last area to go to is a
textbox with merged cells behind it. Problem is that if the worksheet is
protected the tabbing does not work right (goes to the last merged cell with
the clickboxes and skips down a row to the textbox below the target textbox.)
When unprotected the tabbing works great. All cells (merged) are unlocked
that resides behind the textbox, does anyone know what causes this. Is there
a work around for this?

Thanks

Linda