How does the system handle capital call calculations when previous commitments have already been fully called? Does it automatically prevent additional calls, or is there a way to override this for specific investors?

All LPs must be on the same capital call schedule. If they are not, that poses major fiduciary and ethics related challenges. In the event that an LP pre-funds their entire position, their money would get accepted into an escrow bank account and the fund would call the same % as all other LPs on the escrow account.