There is a problem with your code that may be related to your issue.
You are not running a filterbank, you are running the same two filters over and over again, which is a different thing. Since the filters are not pure functions, you can't put them in a loop and expect them to work as if each iteration was independent from the previous.
If you want a filterbank, you have 3 options:
1) Use separate filters, no loops.
2) Use a filterbank opcode.
3) Use a recursive UDO.
best
Prof. Victor Lazzarini
Maynooth University
Ireland