There are so many variables that can cause a snake to regurgitate. First, make sure your Taiwan's environment is in right condition(temperatures, humidity, etc).

If all that is ok, then definitely try a smaller prey item. Currently my big girl is ten years old as well, but can still take f/t jumbo rats. However, I have a couple of other beauties that regurgitate if the prey item is too large. Good Luck!
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"El Respeto al Derecho Ajeno es la Paz" - Benito Juarez, 15 de julio de 1867