what’s with things selling out the second they go back in stock?

I’ve been waiting a very very long time (years) for the replacement filter for the outsize vacuum to come back in stock. A while ago i received the email it was back in stock, hours later when i opened it, it says it was out of stock already. So i waited longer. Saturday i received the email & minutes later i opened it, saw it still said in stock, got excited, ordered it, a couple days go by and i received an email that my order was canceled because it was out of stock due to high demand. This is ridiculous!! There has to be bots buying up these filters the second they drop, its incredibly frustrating because as a customer i NEED a replacement part and it just seems like thats never going to happen at this rate. Dyson needs better software to block these bots so that customers have a freaking chance! I want to just throw the dumb vacuum into the trash thats how frustrated i am that this keeps happening. Makes me not like the dyson brand & i dont want to support them anymore.