I am still seeing this issue in 18w20c. If you use an empty bucket to remove water, it will work as long as the depth is a single block. If it is more than a single block it removes the water source and cannot be replaced until the depth is brought back to a single block.
As you can see in the image, there are three missing source blocks in a depth of 2. At a depth of 1 in the foreground, you can remove a source block and it fills back in as normal.
Also to note is that you cannot empty a bucket in an ocean/river if the depth is more than a single block.
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I am still seeing this issue in 18w20c. If you use an empty bucket to remove water, it will work as long as the depth is a single block. If it is more than a single block it removes the water source and cannot be replaced until the depth is brought back to a single block.
As you can see in the image, there are three missing source blocks in a depth of 2. At a depth of 1 in the foreground, you can remove a source block and it fills back in as normal.
Also to note is that you cannot empty a bucket in an ocean/river if the depth is more than a single block.