This is common. The way LC's accounting works, thing happen at different times of day.
For example, in the early evening, they pull the "fees" out of your account, and then later in the evening, they deposit that day's payments. Your cash balance drops, and can go negative, in between these two events. I see this all the time.
The cash transactions between LC and folio also happen at some odd time, not even on the day you would expect. I haven't ever tried to track them down exactly, so for example I don't know whether folio fees come out at the same time as cash comes in from sales, or if there's a time skew on that too. I wouldn't be surprised to see another skew.
Once there are folio transactions "in flight" it is very difficult to reconcile the cash accounting. You can't just subtract out the last few folio transactions, because they don't complete in the order you placed them. I complained to LC about this once, and they suggested I stop trading on folio for a few days so there'd be no transactions in flight.

As I said, this makes reconciliation difficult. They history page shows dates but not times on transactions, so it isn't easy to figure out. If there are only LC transactions, I think I understand it all, but once there are folio transactions, its really messy.
Aside: Not the way I would have designed it. I think one of the basic requirements of accounting and reporting systems is that they should be reconcilable. You have to be able to do the equivalent of "balancing your check book" using what they provide.
...but its the way it is.