Click and drag sketch enitities in a drawing behaving oddly

Hello,

I'm working with SW Professional 2019, SP5.0

Recently I've been encountering an odd behavior whenever I try to drag a sketch entity while working in a drawing.  As an example, say I sketch a rectangle.  If I then click and drag a corner of the rectangle (i.e. a point/vertex), it behaves how I consider to be normal: the vertex goes wherever I move the cursor and the lines in the rectangle adjust their length to stay in contact with the point.  However, if I try to click and drag one of the sides (i.e. a line) I get the following error message: 

If I hit yes, it'll cut the line out of the rectangle and and copy it to the location of the cursor, so I end up with, say, a C shape and a separate vertical line.  If I hit no, it makes a copy of the line at the location of the cursor, so I have the same rectangle plus a new line off to the side.  And nothing happens if I hit cancel.

I'm used to dragging anything behaving more like the way vertices worked above and it all used to behave that way when SW was first installed.

There must be a setting that got tweaked somewhere, but I'm not sure what it's called or where to look for it.  Anyone have any insights?

(Here's what it looks like when I'm dragging a line^^. The screenshot didn't include my cursor, but it's centered on the yellow preview line.)

Thank you,

Grant