I discovered the following transfer balance bug. First, my lending screen:

And on the transfer screen:

If I try and transfer out the $27.74, I get a useless error:

Eventually, I was able to track the discrepancy down to a dispute on my activity screen:

As you can see, the red arrow points to my real total (including the processed dispute), while the blue arrow points to an earlier total. It looks like they're using two different standards for calculating account balances. Come to think of it, depending on how they're doing things, this bug might prevent you from transferring out cash under different circumstances.