This part is really hard to believe. I briefly worked with radar systems (though nothing classified) These systems are all ancient and janky don't just integrate like lego. You can't just take a radar feed from a drone and feed it into the control system of a cruise missile lol
Even AEGIS systems can't really do that effectively - let alone systems from two different countries (cutting edge military stuff is tech wise in like the 90s at best)
It's not impossible, and it's wartime.. So maybe some Ukrainian engineers hacked something together - but I find this part very unlikely
To me it seems much more likely they got a radar bounce back due to a freak weather phenomena