This could be because they might not be doing EPI (Early pay-in) of shares to the depository against sell transactions. NSE recently issued circular which said that to give credit of sale proceeds on same day, EPI has to be done. If EPI of shares is not done, the credit recieved from selling these shares cannot be used for trading.
Since we do EPI at regular intervals, this doesn’t affect us and we provide 80% or the sale proceeds instantly when the shares are sold, while remaining 20% are available on the next day.