Moka pot valve constantly letting steam out.

I have a bialetti Venus moka pot (6 cups) and it recently started to let go of steam through the valve even before the coffee starts to flow, making it difficult to properly filter the usual volume of water.

It started when I did a brew with to much grounds with espresso size grind, but know even with a regular amount (not taller than the basket without tamping), a bit coarser grind and no tamping at all, the valve is open during the whole brew.

I understand I may have broken or loosen the valve, did someone had a similar experience and fixed it? (by replacing or tightening the valve someway)