Can’t make any changes on activity page at /user/[uid]/activity/settings

I'm register on my site as new user, and then I go to /user/[uid]/activity/settings
I was select one checkbox 'don't record my activity when new comment posted' and press 'Save' button. Now I see that this checkbox is selected.

In my proxy log I see:
Posting 268 bytes...
actions%5Bactivity_ignore%5D%5Bcomment_insert%5D%5Bcomment_insert%5D=comment_ins
ert
op=%D0%A1%D0%BE%D1%85%D1%80%D0%B0%D0%BD%D0%B8%D1%82%D1%8C
form_build_id=form-9d88937dbf2c1e256d45b25f6cdf3742
form_token=22a1d7befb9f5610263057e41b9ee40a
form_id=activity_user_settings

Then I unselect 'don't record my activity when new comment posted' and press 'Save' button again. I don't see any changes - the checkbox is still selected!

In my proxy log I see:
Posting 184 bytes...
op=%D0%A1%D0%BE%D1%85%D1%80%D0%B0%D0%BD%D0%B8%D1%82%D1%8C
form_build_id=form-3d3830d706fae6a1a2a5a9cc9cdfa8f7
form_token=22a1d7befb9f5610263057e41b9ee40a
form_id=activity_user_settings

Then I try to select some one else, for example, 'don't record my activity when comment is updated' and press 'Save' - nothings happens! Now there is always one selected item - the first item.

In my proxy log I see:
Posting 352 bytes...
actions%5Bactivity_ignore%5D%5Bcomment_insert%5D%5Bcomment_insert%5D=comment_ins
ert
actions%5Bactivity_ignore%5D%5Bcomment_update%5D%5Bcomment_update%5D=comment_upd
ate
op=%D0%A1%D0%BE%D1%85%D1%80%D0%B0%D0%BD%D0%B8%D1%82%D1%8C
form_build_id=form-9fbacc993b9e3597269711510e955080
form_token=22a1d7befb9f5610263057e41b9ee40a
form_id=activity_user_settings

How it's possible?