You might try taking your images into something like Adobe Lightroom. Lightroom lets you view a library of images all at once as on a light table and make adjustments to individual photos, groups of photos, or all of them. Changes applied to one photo can be applied to others.
I might select two representative photos from each of the different sets and see what I needed to do to balance their differences while preserving as much information as I could. You don’t want to clip either the darks or the lights when making those adjustments, else lose information in those areas.
You mention a ‘step line’ between image sets, but it’s not clear to me what exactly that step is. Horizontal displacement? Vertical? A bad looking blend line in a mosaic?
If a technician has a difficult time locating a tie point so might the software. How much overlap you really need depends on the subject but a lot on your lens as well. The super wide angle lenses can produce tons of overlap but a completely dissimilar perspective that doesn’t match easily.
Some combination of additional tie points along the seam line between image sets could help, and or processing them as separate areas with those common tie points. Masking of one line in the overlap area could help too. Depends on what’s wrong. But my first stop would be working on the imagery.
Steve