Lack of consistancy by various airport groundstaff is not only confusing to passengers but also irritating. Only a couple of days ago I had the same experience with Lufthansa (Eurowings) flights on an CRJ-900. First of all my cabin bag is a soft top type and it meets the carrier's requirements. I have never previously had a problem with it before (including the the same a/c type). Outboud Germany no questions and no problems. On the return from the UK no comment from the check-in agent who saw my bag. At the gate I was informed that it wasn't suitable for the cabin and needed to be tagged for "delivery at aircraft"! The flight was only 2/3 full. Out of curiousity I asked why my bag was suddenly classed as unsuitable. Needless to say I didn't get a satisfactory answer. I didn't waste my breath arguing the point and let her tag it. I took it on board and asked the CC if she had any objection to its size. "That little thing Sir (she was referring to the bag), is no problem at all".