Has anyone ever had issues with lift chairs? Starting to wonder if we should not let her operate the chair?

My husband's grandmother (92) lives with us. Her only son passed at age 26 and my husband and I moved her in with us almost two years ago. The lift chair has been great until recently. I know we have to have one for getting her up and down but sometimes I am afraid that we may have to take away the remote soon. Sometimes she will just raise and lower the chair for about a half an hour. I will tell her that she is going to burn up the motor and then she will stop. Recently we started having issues with her having her walker to close and may bring the foot part of the chair down onto the wheels and then the chair is unable to lower the foot part and the chair starts raising off the ground. Often times she will ask us if her chair is up and she will have it all the way back. There is someone here with her almost at all times but even if we have stepped outside for something or have slipped down the the basement or even the bathroom, I fear that she may get hurt with the chair. Just today she had slipped down in the chair so as she went to get up, she was just about falling out of the chair.