I just noticed something else: The time of the transaction that hasn't been broadcast keeps changing. So, for example, a transaction that was supposedly sent 2 days ago now says that it was started less than 2 hours ago. However, the time for the transaction on the side of the sending address remains unchanged, which is weird.

So, for example, I took a look at a random transaction from one of their address started December 7th, and within their address the correct date is shown, but now it says it was started today under it's transaction ID:

https://chain.so/tx/BTC/b2b8f5163966f059a59d9aa56000a6ec9ab0d3fd58fe66eb628787237be692b9

That means it's not even operating on a proper queue, where we'd expect a first in first out order. Some transactions are confirming fast, while others take days to over a week.