I don't entirely follow the logic of the trip (but I know nothing about shipping). Tromso on the Norwegian Sea, then Klaipeda on the Baltic, now off the shore of Kent? That's very roundabout.
It's easy to come up with explanations involving bad will. There must be some legit ones too. What are they trying to achieve? Did they buy some ammonium nitrate and are trying to offload it for a buyer, but successive ports are saying no? Surely whoever paid and loaded the cargo needed some idea of where and how they will offload it.
I agree also that news report are missing to report on what is the most interesting part to understand the problem:
What was intended with this shipment in the first place? who is responsible for it? Regarding current international sanction, what was this ship doing loading or unloading in Russia and then going to any cost in Europe.
Also, wouldn't it possible to unload it by smaller units with smaller boats why at the see?
Bad weather is a reason to avoid bad weather. On the scale of a long voyage, weather is "local" and can be avoided either by picking a different route, or a different time (potentially hiding in a man-made or natural harbor where the ship is less exposed to the waves and weather due to the surrounding terrain).
See also "Ruby has previously been turned away by Norway, Sweden and Lithuania, as well as facing restrictions imposed by Denmark while crossing the Baltic Sea, because of her dangerous cargo." from this page:
It's easy to come up with explanations involving bad will. There must be some legit ones too. What are they trying to achieve? Did they buy some ammonium nitrate and are trying to offload it for a buyer, but successive ports are saying no? Surely whoever paid and loaded the cargo needed some idea of where and how they will offload it.