(a) I assume that any destination unloaded product which had visually thawed out (somewhere) was now fully refrozen since otherwise there would be no argument as to one origin of problem.?
(b) I do not know yr production flow, ie whether shrimp initially frozen in bulk then later packed frozen into final packaging or directly frozen in the final packaging. Traceability if required likely to be easier with latter assuming appropriate labeling on the product boxes and/or outer cartons.
(c) Are there multiple temperature readouts on logger record or just one trace ? I’m only familiar with the latter, often stuck somewhere near the air blast coil IIRC.
(d) Was the container loaded/sealed at yr factory ? “No” introduces more variables of course.
(e) Is the shrimp directly packed into cardboard box or within an inner plastic bag ?
I can only think of approx 3 theoretical possibilities depending on “flowchart”–
(1) Production/Freezing/Storage. Assuming the container lot has a variety of production dates and/or packing dates it is conceivable that there may have been a freezing/packing/storage “event(s)” causing certain batch(es) to thaw/refreeze prior to loading into container. This might not show until container reaching destination although one would think/hope likely to be picked up during loading.
(2) Loading. Some kind of event during loading stage(s), eg delay. Also relates to (d) above.
(3) Voyage. The container cooling system may have sporadically failed and/or the data logger might be located incorrectly within container or be simply incorrect. IIRC the container supplier typically (somehow) validates the cooling temperature achievable prior to delivery to customer and records the results. I’m not sure exactly how the container cooling system works but presumably like AC units.
If only the outer layers in reefer have problem and same product freezing date(s) in the inside looks OK it rather points to the reefer.
If all the product from only certain specific freezing dates has a problem regardless of container location, maybe the opposite conclusion.
Offhand, I suppose the thinner box will give poorer insulation but, IMEX, IQF tends to get hit pretty fast in the best of circumstances. The different box style may separate the freezing dates though ?.
I’ve never personally met this problem so I’m not too sure how reliable data loggers / container records usually are, pretty good one would hope from an insurance POV.
It's a tricky one.