One seemingly trivial example ... tai no henko ... when nage simply presses forward they run into all kinds of power or 'resistance' which is just a moderately connected uke. Uke does nothing except maintain their balance and posture (internal connection if you will) and nage cannot do the most simple of movements. This is true even when uke is a small child and nage an adult. Usually 'stupid' nage just powers through the resistance - easy to do against small children but not so easy with adults.
This is not resistance in the slightest ... nage is simply doing the technique completely wrong. Amazing to watch the uke that simply 'folds' and lets nage do the technique anyway ... fast forward a few months and nage has learned not one danged thing. Fast forward a few years and there is a spanking new shodan that cannot even do tai no henko correctly. Since tai no henko is a foundational drill (in Iwama lineage anyway) this is a huge problem and must be set aright from day one.