Vintage Canon AE-1 35mm SLR Film retailer Camera for parts/repair or display

Product Name: Vintage Canon AE-1 35mm SLR Film retailer Camera for parts/repair or display
Cosmetically this camera is in excellent condition. The only issue with this camera is that the mirror gets stuck. Sometimes it will come down on its on after some time and sometimes you have to press the battery check button retailer in order for the mirror to come down. I've checked with a battery again and now the mirror doesn't seem to get stuck anymore. Now the shutter release button doesn't seem to be consistent with activating the mirror up & down. I'm not sure if I don't have enough juice in the battery or what. This is beyond my knowledge and may be an easy fix for someone with experience. I recently purchased this camera off of Mercari. So selling as is, for repair/parts or display.