This happened on first turn on the replay ive attached. Im finding the cardian monsters a bit dodgy the ones where you can special summon a cardian if drawn, there are multiple (moon, crane & calligrapher). sometimes it allows me to special summon it most of the time not.

is this a bug?
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It is not a bug.
The effect of Flower Cardian Pine with Crane in question is this:

If this card is Special Summoned: Draw 1 card, and if you do, show it, then you can Special Summon it if it is a "Flower Cardian" monster

But the card you draw is Flower Cardian Zebra Grass with Moon that has the following text:

Cannot be Normal Summoned/Set. Must first be Special Summoned (from your hand) by Tributing 1 Level 8 "Flower Cardian" monster, except "Flower Cardian Zebra Grass with Moon"

Since Zebra Grass with Moon has to be first summoned by its own procedure, Pine with Crane cannot summon it when you add it to your hand. You have to pay attention to the Flower Cardian you draw. Many of them have restrictions on how to be summoned.