[Cannabin0l]

I just noticed a portal missing a block heightwise, and the portal stayed pieced like so above, and I fill in the whole side with smoothstone and it still works like a normal portal. I don't know if it's really a bug, just odd and I've been seeing these tiny sub-portals all over, don't really understand them or how a portal gets to looking like that. :/

[FaeynHeart]

Im not sure either, but I saw a messed up portal like this in the nether and it saved me from starvation

[Prodigy9]

I'm not sure how they're formed, but it might have something to do with the channels. At one point, the portal in the nether to spawn city was perfectly normal on one channel, but had only one purple "portal" block on the other channel (despite having a complete frame). Standing in that one block still allowed the portal to work as usual. Maybe when a portal frame is destroyed, the automatic removal of the corresponding portal squares doesn't always sync between channels.