Drill a small diameter e.g., 1/8 - 3/16" very shallow hole at the end of the cracks to stop their direction of travel. Then use a vinyl repair kit or a silicone to fill the cracks. If you find something with a similar grain/texture it can be used to imprint the sealer as it dries.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer