Location: California. Manager is clocking me out without my knowledge before I stop working

Location: California I work at a retail/grocery store in which I am a keyholder. In January I began to notice I was being clocked out by my manager, not by me. I thought it was weird so I wrote it in my messages to myself. Then, in June of this year, I saw on the cameras after the fact that I was being clocked out by my manager and not being told but was working along with everyone else who didn't know they were clocked out for about 15 minutes. This happened 2 days in a row. I don't know about any other days, but those 2 for sure. I brought it up to my boss who talked to my manager and then me and said that it was a "miscommunication" and that everyone knew they were clocked out and "volunteering" to work past their shift to get the store ready for the next day. No one else knew they were being clocked out, I know because I asked them. I don't know what I can do so I'm looking for advice. I am pretty poor so I don't know if there's any way to get a lawyer for cheap or anything like that. Thank you for your time.