Grafana alert state changes unexpectedly multiple times

Could you help to figure out why I am getting alert cancelled but then raised again in couple of minutes even would expect that based on alert query the last value should not be under 90 % (I got email notification telling the value to be 0.892 -> 89,2% in the first Alerting state after the ok state). This ping-pong effect continues for a while and then settles down.