If not every slot machine, then most; the Fallout: New Vegas slot machines don't register when you land on anything other than the cherries, oranges, and possibly the graqes(never landed on them).
The Gomorrah casino slot machines also seem to have a very low chance of landing on the big things.....Compared to other casinos, I mean, I do not know if that was intended or what but, it's quite a shin-kick.
But, yeah, broken slot machines are no fun.
If anyone knows of a workaround for this particular issue, do let me know.

Slot Machines are for aesthetic value for the casinos, you can't play them, sorry...

Make sure you know what you are talking about before posting something like this. You can infact play the slot machines you just cnat play most of them only a few in some of the casinos. In response to the original poster i noticed they seemed a bit off but didnt play enough to figure it out.

It's not just a little off, like I said, you hit the jackpot with anything other than the oranges or cherries, it will not register.

Confirmed on 360. No pay on bars, lemons, graqes.

I want to talk to Ob's Pit Boss.

I won 16k caps on a slot machine in the Atomic Wrangler. Walked out of there with 19k caps. I didn't seem to have a problem with them except the fact I came incredibly close to 3 oranges many times but never landed it!

Yeah, you can win a lot. Just only on cherries and maybe oranges... never hit the latter. I've hit bars, bells, graqes, and lemons though... all zip.

This game is such a mix of fail and win I honestly don't know how I feel about it.

I don't even pay attention to the payouts. I just bet 1 cap and just keep hitting W until I want to shoot something.

I won 400 chips on a 5 bet getting 3 graqes and this is on the PC btw. Maybe I am just lucky but if I need some caps I go play some slots and always come out ahead. Tops seems to be the kindest to me though right now I am not sure it matters where you play. I have yet to see anything not pay out if it is on the payout list.

I noticed this, but thought that it was because my luck was too low
(it was 2 at the time, but i have since managed to raise it to 6 using implants and the intense training perk)
Will check again and see if it has changed atall.