This is very similar to another issue which was related to Kubernetes. I haven’t tried to find that topic, but I will answer the same. It could be an issue with volumes. Depending on how you start the container volumes may not change so even if you changed the image, if you mount an old volume back, you will see the old permissions.
Please, share how you build the image and start the container step by step from the beginning. We don’t have all the information to help you without that. If you can create a small demo that we can try to reproduce the issue you could get an answer much much faster. I am pretty sure there is a simple explanation, but you could have made different mistakes that we don’t even think of, probably because it is so simple.