As teak wood is a natural material, small cracks or splits can sometimes appear as a result of changes in humidity and temperature. Although slowly kiln drying teak furniture helps to significantly limit checking, teak is natural and will expand and contract (breathe!) in our varying weather conditions and absorb moisture in the air which makes it swell a little.
A process called checking may occur as your outdoor furniture adjusts, very slightly, to its surroundings. This can result in small hairline cracks developing, usually on the end grain sections. The cracks come and go, and will eventually settle. Most importantly, they do not affect the strength and performance of the teak furniture in the long term.
As teak is exceptionally strong and durable, it is highly unlikely that these cracks/this end grain checking will disrupt the strength or structural integrity of your teak furniture.