After the American president election day, the Australian share market had a big drop in most share prices. A registered tax agent thought it was a good opportunity to trade for a gain, but he did not have sufficient fund. Meanwhile in his business trust account, two tax refunds for recently lodged two tax returns had just been received, so he transferred those refunds and purchased large quantity of shares. Two days later, he sold off those shares with a gain, and then transferred the refunds back to his customers' bank accounts. 

Identify and explain any ethical issues in respect of the tax agent's conduct. (minimum 100 words)