This is quite possibly the explanation. However it begs the question as to why Russia is targeting cruise missile strikes right on the border with a NATO country.Possibly could be remains of Ukrainian s-300 anti air and its target (Russian cruise missile)
Extremely provocative and extremely dangerous and I can see Poland as a response pushing forward their AD systems right up to the border with Ukraine and updating the ROE of their gunners and pilots to engage anything hostile upto 70-80km into Ukraine, effectively creating an enforced NATO air exclusion zone over Western Ukraine.
Nice one Putin lad