Guard Stop State

Hi there, I'm working with a manufacturing robot and I have some problems with guard stop state. Every time I blocked the light screen the robot will be in guard stop state, and once I get out of the light screen the guard stop state would be removed. But sometimes the guard stop state still remained, it happened when I get in and out of the light very frequently. I checked the safety circuit, it's closed once I got out of the light screen, but the robot was still in the guard stop state. I'm wondering what caused this issued and is there any solution for this?