It's hard to tell from the photos but the leaves on your problematic aloe seem different to your "other aloe". Perhaps they're different species and thus will have different different habits ie. not supporting themselves well.
It looks like you have have three aloe babies growing in that one pot. It'd be better if you lifted them into separate pots, placing them upright so they're roots have the chance to support them upright. To do this, you should lift the whole plant out and brush off as much soil as you can. Then carefully separate the baby plants from the main plant, the best way is to cut them off with a sharp knife.
As to your 3 suggestions, you should rightly be wary of overwatering Aloe since it can lead to root rot. It doesn't look like it's suffering from this particularly. If I overwater my aloes I see a build up of fruit flies around the pot, suggesting something is rotting.
You should be equally careful of underwatering, especially if your soil medium is peat based. Aloes like to be dry whilst they're dormant through winter, however if you let peat dry out then you'll never be able to rehydrate it. Which is a mystery to me why it's often marketed at cacti / succulent growers?
I believe growing space is the issue here, but technically not due to pot size. Aloes form shallow horizontal root systems, so with 3 plants crowded into one pot they're likely to be in each other's way. Certainly transplant them into bigger pots, but think wider not deeper.
