I think it has been stopped. My guess is that, at first, Russia was caught unawares because there was nothing in that area that would affect the current conflict but Ukraine works more on media victories than military victories.

The incursion was slowed right down almost straightaway. Only small changes have happened since. Russia installed three lines of defence between the incursion and the city of Kursk itself so then it did not matter whether Ukraine moved further inwards or not. Eventually they would find three lines of dug in Russians.

Ukraine used its best troops which meant that they were not available to defend Pokrovsk which is a major logistics hub. Militarily, losing Pokrovsk is much worse than losing some of the Kursk oblast. Russia pressed head with its advance on Pokrovsk and it went incredibly quickly. They are getting quite close to the city now.

Russia has reinforced the Kursk region and, over the last three or four days, Russia has taken back about a dozen conurbations. So it now looks as if they are about to push Ukraine out of Russia in the next few weeks.

My guess is that Ukraine hoped that the assault in the Pokrovsk direction would be halted as Russia would move troops to Kursk but Russians are chess players. They saw the longer term consequences. Being invaded can be made to look bad in the western media but, on the ground, taking Pokrovsk is be a much bigger win.