There may be various reasons why rice cookers can pinch rice, here are some possible reasons:

1. Insufficient water: If the amount of water added is not enough, then the rice will become hard and easily pinch.

2. Insufficient cooking time: Most rice cookers have the function of automatically adjusting the time, but sometimes the time may not be enough, resulting in the rice not being thoroughly cooked.

3. Internal malfunction of rice cooker: If there is a problem with the heating element inside the rice cooker, such as overheating or insufficient heating, then it will affect the cooking of the grain.

4. Different rice varieties: Different rice requires different amounts of water and time to cook, and if different varieties of rice or ingredients are used, it is likely to lead to cooking of entrapped rice.

5. Incomplete cleaning: Sometimes, the grease or impurities from other ingredients remain inside the rice cooker, which can affect the cooking of the rice.

6. Replacement techniques: Some beginners are not skilled enough in cooking techniques or do not follow the rice cooker instruction manual to recommend the use of the correct cooking mode, resulting in undercooked rice or entrapment.

In short, there may be many reasons for rice cookers to trap raw rice, and you need to carefully check and eliminate the above problems to better cook delicious rice.