It changes the tone, I think.
When you say "I see a few problems" you're saying that there are definitely some problems and they should probably be addressed.
When you say "I see few problems" you're saying "I don't really see many problems here at all and the problems that are here are not that important.
I'm not sure, checking Reverso Context, it looks like it's possible to use несколько for the latter but it seems like мало is far more common.
For me in English there is no real difference between "I see a few problems" and "I see few problems" depending in the intonation both can mean "there are only a few problems" or "this is not ready there are still a few problems" in this case which one are we addressing?.