They discovered the problem. Waited long enough to see how extensive the problem was. After whatever investigation process there was, it was determined that they were just manufactured poorly. Design error or manufacturing error? More testing. Now that the true issue is understood, how to fix it. Iterate changes to make new replacement better than original design. Cool. Now, find a factory and get in their queue to manufacture the thing. Receive shipment via literal slow boat from China. Distribute parts, arrange repair mechanic appointments, etc.
I'm not defending the situation I find myself in, but if you honestly can't think of "what's taking so long", then I'd suggest you're just not trying at all. Maybe you have no experience manufacturing something, so that might be out of your wheel house. It's not like someone can just say 'git clone bicycle parts' or 'npm update bicycle parts'