I find it hard to say anything. The best way would be (as suggested on my first reply) to make a video describing the problem.
It might be a non issue, it might be something that you have placed incorrectly.
If you do decide to video:
- Please show us you locking the portafilter, and any noise it makes.
- Please film underneath the group, so we can see the shower screen and the group, specially where the portafilter engages;
As mentioned before, make sure everything is clean (clean the group with a brush and water). Also make sure the gasket is not upside down.
Looking forward to your video. But without it, I’ve run out of ideas.