I recently bought two gliders to be cage mates with Echo my glider who had cage mates before in a previous home. Their owner told me they crabbed at each other even though bonded. They run around seemingly in a playful manner like tag. But they often crab at Echo though each other as well. Sometimes they swipe a paw while running like tagging and run the other way. They don't always crab. Should I be worried or is it playing?