That is correct, there were border raids which prompted the invasion, but the Sino Soviet split is what caused the worsening relations which led to that. Basically, the invasion was cringe, even if there was some justification for it, but what was more cringe was the repudiation of Stalin and the revisionism in the USSR that followed by corn boy.
This was also evident when they had that TOW test which should have been a simple point and shoot but the missiles were either so old or faulty they just fell into the ocean right after launching.