OK I have investigated at length the problem you reported, and have provided a fix in version 3.6.7 of the parent plugin.
Thanks again for spotting this. There was another bug in the algorithm that sums fees for the balances. This was introduced in 3.6.5 while attempting to fix another bug. The algorithm now correctly sums fees for all kinds of transactions, i.e. deposits, withdrawals, internal transfers and exchange trades.
Due to the bug being fixed now, you or your client may notice more negative balances. This is because withdrawal fees were not subtracted from user balances during the time between 3.6.5 and 3.6.7. My sincerest apologies for this.