oil bug?

[Deliphin]

I got buckets of oil from a nearby oil lake in an extreme hills, and took them home. I put them in an empty tank which was connected to the back of a refinery, and the front of the refinery attached to other tanks. I emptied my buckets and activated it. Today I got more oil from the same lake, but this time when I put them in the empty tank, my buckets weren't emptying, it just filled and filled. I thought I duplicated it, so I turned on the first redstone engine, and the bottom tank instantly emptied. The top two were full still, but nothing flowed through the pipes. I broke all the tanks and replaced them, and then when I put oil in them, my buckets stayed full and it emptied about every half second. How can I fix this, and what caused it?

EDIT: My crappy setup: http://imgur.com/YKaOcpa

[Epikos1994]

maybe it was a bug, are you sure you collected from a source block?

[Larawyer]

i think its a bug as it did it to me the only way i got round this was to basically empty the buckets in a hole and use a pump also i had to break a few tanks and put them down again before it finally filled them

[Deliphin]

maybe it was a bug, are you sure you collected from a source block?

1: It was now placeable when I put the take in a different location connecting to the waterproof wooden pipe. Also, how can you collect from a non-source block with a bucket? I heard you could with quarries, but our quarries never went through oil yet.