The "Push to Brake and Push to Release" mechanism requires a regular maintenance. By each push of the paddle, the centre plastic sleeve turns 45 degree and sets the centre metal pin up and down between "lock" and "release" positions. When sand or dirt gets inside, the centre plastic sleeve stops turning and malfunctions the brake. So, you just need to take the brake off the buggy by undoing few screws, then disassemble it to clean.
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