The client thinks you are still casting a spell, the OP_Mana never gets received(At the end of casting any spell, you get an OP_Mana with how much mana you have left.. thats how using jboots or another click item refreshes the client's mana to the server value)
The problem in tracking down the bug, is you can never reproduce it when you want to
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++[>++++++<-]>[<++++++>-]<.>++++[>+++++<-]>[<
+++++>-]<+.+++++++..+++.>>+++++[<++++++>-]<+
+.<<+++++++++++++++.>.+++.------.--------.>+.
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