Pawel,
While I suspect Tim makes a valid point I look at your part and suspect that certain features are running into or over the edges of others. So I suspect that what you're trying to do is to use sketches, associativity or a combination thereof to maintain those relationships between features such that when the dimensions are edited the model will update and the blends will still run.
As Tim says we could be wrong, for all we know most of what we're looking at could be a styled surface from a sewn and trimmed sheet that we can't see in the feature list, and which might explain a higher than expected feature count.
There is an old principle often quoted in engineering, which in english is abbreviated to KISS, for Keep it Simple Stupid. It means that too many features could mean too many things to go wrong. Thus the reason that you have many problems may be an un-diagnosed conflict between two or more associative features which are refusing to update in the background because some change you have made to a basic dimension via your sketch results in an invalid outcome, meaning geometry that can't be resolved. Sometimes it happens, and the best advice is too keep things simple. Even if that means that you have to ditch some of the complexity in favor of models that need you to manage the updates more manually then maybe you'll be better off doing it that way if it is simpler for you.
Best Regards
Hudson