Bonding is a somewhat more complex subject... that a simple YES/NO answer.
People who say NEVER and ALWAYS on this subject are both wrong! It is a fact that there are old boats that are bonded that are in excellent shape, and there are old boats that are not bonded that are in excellent shape.
The more complex the boat, the more bonding is likely to be helpful, and anybody who categorically says NEVER BOND without having ANY information about your boat, you can pretty much ignore.
When you added a bonding circuit you added routine maintenance
and testing to be sure it stays as it should be.
This is a complex topic, let's start with your bonding system. The following information is needed (and likely more too) to diagnose your problem. As you might guess from the list of questions, you are asking a question that is pushing what can be done without hands on testing...
What kind of boat?
The thru-hull that has the issue, where is it? What does it supply? How many thru-hulls are connected to the bonding system?
What is connected to the bonding system OTHER than thru-hulls?
Is the bonding circuit connected to a zinc? Size of the zinc, and its location? Is the zinc in good shape and is the connection KNOWN to be good? How long do your zincs last?
Is your bonding system connected to battery
negative? Is that connection at ONE place? Is it possible there are other connections to battery
negative you do not know about? Have you looked for them?
Do you have any ground leaks
? If you say "no" how did you test?
Do you have an AC system on board? Are you plugged into shore power
? Do you have a galvanic isolator
or isolation transformer? Is your AC Safety
ground connected to your bonding system?