Predictons same with StockTradingEnv, using 1 stock

**Describe the bug**
I am using your your colab guide here https://github.com/AI4Finance-Foundation/FinRL/blob/master/Stock_NeurIPS2018_SB3.ipynb

I am training the model with PPO agent and using DRLAgent.DRL_prediction to make predictions. Also I am using only 2 stocks ['ADS.DE', 'ALV.DE']

I didn't change nothing inside StockTradingEnv. I just removed from the Environment instantiation for the test the turbolance and risk params
These two.

The rest is all the same.

I added a print in DRLAgent.Prediction to print the action while predicting on test data.

This is the result: https://nekobin.com/hapodiniba

Why most of the time the predictions are same? And why if I only use one stock predictions are always same and never change ?