I have found what I am certain is a bug in wolfram cloud. I generate the following code in Mathematica and then save it to the cloud.

Clear["Global`*"]
List@@Expand[(1+x)^6]/.a_. x^b_.->{b,a}

This initially runs correctly in the cloud notebook. But if I edit the notebook on the cloud, for example changing the exponent in the expansion from 6 to 7, then running the notebook results in a syntax error. I looked at the text on the cloud after editing the notebook and the " _." has been converted to separate objects, "_" and ".".