There are two cases where alerts can be expected to fire late. Note that in both cases the root cause is not a limitation of Drakdoo.
Especially on Android, certain devices can use aggressive battery optimization/power saving modes that prevent the app from receiving and processing push notifications. Please alter your device settings such that Drakdoo is not hindered by these modes.
The required steps to configure this differs per device. There are various tutorials available online that explain how to do this. We recommend to follow this guide. Note that this guide is for a different app, but the procedure for Drakdoo is exactly the same.
Alerts that require tops & bottoms to form, such as Divergence and Highs & Lows, by definition fire late.
You can only conclude that a candle represents a top or bottom a few candles after the top/bottom has been formed. The reason is that at the time a new high is reached it might just as well be the case that the next candle will go even higher. Therefore, you can only conclude that a certain price point is a top/bottom after the price starts moving in the opposite direction.
Therefore, a top/bottom is only regarded as such if it is higher/lower than its surrounding candles. For Divergence, by default, this requires 2 candles to the left and 2 to the right.