Need some help with practise

[lemons]

So I haven't had much time to practise this year (about once a week) and recently I've started practising some pieces again, but I'm getting this problem where the more I practise the worse I get.
For example, for Fauré Barcarolle Op.26 the more I practise the more uneven the rhythm becomes, and Scriabin Etude Op.8 No.12 I've never really had problems with the octaves but now its impossible to play those semiquaver octaves without missing notes or playing the wrong ones. The badder it sounds the more I practise to try and fix it, and the more I practise the worse it gets.
Does anyone have tips for situations like these? Should I just leave these pieces for a while and try again some time later? Its really quite frustrating. (I'm teacher-less right now so there's no one that can really help  )
Thanks!

[indianajo]

This belongs in the student area.
My skills deteriorate when I spend the summers away from the piano (due to the ozone in town) and at other times when arthritis forces a break.  During the re-acquaintance period, I can find I am making some consistent mistakes.  My kinesthetic sense of where my hands and fingers are develops flaws.
The solution is to slow down and relearn the faulty part one hand alone, to recalibrate the brain's sense of where the fingers are.  A couple of dozen repetitions exactly correctly over a few consecutive days, seems to give my sense of competence at some piece another life. Then I can go back to where I was, since I already had some sense of the piece memorized.
Another barrier occurs when I am getting fast enough I can't read the score anymore, and don't really have it memorized.  In that case slowing down two hands together is good enough, with some additional pencil marks on the bad notes to focus my eyes on exactly what I need to look at.  When I get across this barrier, I have the piece memorized in my lower brain, by muscle movements, and  need to look at the score only to track how many reps of which particular theme comes next.  This can be summarized by some coded notes on a card, and that memorized some other way, to eliminate my need for the score at all. 
I hope you can find time to get up to a couple of reps of the difficult parts a week, saving time by not playing the parts you have learned already. 
Have fun.