Hi My view of it would be that if there are transactions then the company must be active. Sounds a bit suspicious to me though, have you carried out MLR checks.
Does seem strange but there may well be a good explanation, never judge a book by its cover!
The company is dormant as it has not traded or provided a service for a fee. Strangely enough, if you own a leasehold flat and pay service charges to your company to then pay the costs related to the communual areas, this is also seen as dormant! I know you won't believe me but its true!
Per Companies House guidance, a company is only dormant if the 'only' transaction entered into the accounting records is the issue of subscriber shares (in the first year) or non-significant costs that are required to keep the company registered at companies house.
The company in my opinion would be classed as a non-trading company. A company can be non-trading in the sense that it is not doing business. However, it may still have other accounting transactions going through its books, which means that it is not dormant in a legal sense. Non-trading companies are treated differently to a dormant company which can simply file form DCA each year (a non-trading company can't do this). A non-trading company will need to file abbreviated accounts, although they will have little information in them.