slur problem after copying?

Ah I see. I didn’t realized that I unintendedly used different voices.
Thanks

Whilel trying to change the downstem voice in bar 1 by selecting all 3 notes with mouse clicks and then choose via right click to change the voice into the 1st downsten voice I got an unexpected result. The triplet gets deleted. The last of the 3 notes goes into the next bar.
Is this intended?