None of the items in isolation are huge red flags. But if they bought these companies for the "tech", then why are they still paying so much to make their drones? Seems like they bought companies that can be repackaged as a story to be sold to investors, while they overpay for actual tech from 3rd parties. Raw material prices are slightly below revenues - hard to make a profit that way.
Just read the financial reports. You'll quickly find it hard to explain your opinion to yourself :)
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