I thought I saw that @bravenel posted something about a fix for this issue, but I can't find it.
The first screenshot below is a rule that I cloned from another rule. I deleted the one line shown with the Xs, the second screenshot was the result. It caused three lines of broken actions, each having nothing to do with the line I removed, at least nothing that is obvious to me.
I am moving some rules I have in webcore into RM. The original file is a dishwasher monitor routine and I am converting it to a Dryer monitor. The original rule used a Power plug for monitoring and the second will use a acceleration sensor, but the basic setup is the same and I wanted to just clone and edit.
I had already done this once and fixed the broken actions. I deleted each broken action before I did anything. I then added back the lines that got removed. I was about to save it when I realized the wait for event condition dryer sensor inactive had been deleted from wait event. The first time I did this I wasn't sure when it happened. When I did this the second time I found that when I deleted the WAIT for condition on the power level of the dishwasher plug it removed the condition in the wait for event on the dryer sensor. The line was still there, it just had no event to wait for. When I tried to edit the line and put the event back it caused a condition where I had to just start over and build the rule again.