Ok, this problem is my nightmare from the time I started working with xpages.

Sometimes it happens that user clicks a button, refresh is done but the data sent are ignored.

I've noticed that when this happens new viewid is returned (I mean the value of hidden input named $$viewid) 

To me it seems like an error occurs and the old viewState is discarded and new one is generated instead.

But there is no error message in any log (domino console, data/IBM_TECHNICAL_SUPPORT xpages log, expeditor logs) .