Using a linked checking account with a brokerage account
I'm considering using the linked checking account feature, which I've never used before and I want to make sure there are no gotchas.
I tried on a test account adding a linked checking account to a brokerage account (with Fidelity, if it matters) with over 10 years worth of data and it did not go well. After churning for about 15 minutes, I got the message
Not sure which data it didn't like. I see that what it did is change all cash transaction in the brokerage to transfers to/from the cash account, which makes sense. But it also showed a balance of $150,000 cash, which is nowhere near what I have. So whatever transactions it couldn't convert clearly caused an issue. If I did this, I think I'd open a totally new account, so it was linked from the beginning.
When updating the account in Quicken, do I just update the brokerage account and then the cash transactions will show as downloaded transactions in the cash account? Does that all work the same, so that if I manually enter a transaction in the cash account (say, I paid a bill), then it would 'match' the download transaction?
If I manually enter a transaction, say a buy or sell, in the brokerage account, do I have to make sure to transfer the cash to/from the linked account? Will buy/sells of money market funds count as cash?
Is there anything else I need to watch out for that will surprise me?