PlayerPrefs in WebGL not saving or deleting

After a while the game was working fine in WebGL, suddenly the PlayerPrefs got "stuck" in a particular state. I'm writing and deleting, and saving values, and get no errors that i can see in the browser (chrome). But after i refresh the browser, i still get the same state as it was before.

The different keys are independent, and should not effect each other, none of them is saved in the new state. The game works fine for other users and on different browsers. It looks like a hard to catch/reproduce bug.

I've tried adding PlayerPrefs.Save() after each modification, it didn't help. Another team member had similar issues, but we assumed it was something else. After changing the keys names, it worked fine for him, but i'm afraid it will happen to a live user. I can change the keys names in my version, but i'm afraid to lose the reproducible bug.

Any ideas?