Occasionally
Once In A While
adverb
Something you do accidentally is hopefully something you do occasionally or once in a while.
For the reading, think about the word 弾 (たま), which means bullet, and how you occasionally shoot people with bullets when you're out hunting... but not too often. Dick Cheney level.
偶にぎっくり腰になるんですよね。
I strain my back every once in a while.