100-400 issues in tropical weather

I've been in the indian ocean region earlier this month and I brought along my 100-400 just in case I had the opportunity to go for some birding...

The lens behaved perfectly well (much as expected) until a few days after arriving there when I saw a small and thin rubber material on the barrel... couple of days later, I realised that it came from the locking ring as more of this material was visible and the lock wouldn't work any more ...

On top of the above and, obviously the weather is very humid and considering the lens is not weather sealed, I have a double question:

Should I send it to canon to repair the lock (is this possible BTW?) ... and ... Is there any "preventive maintenance" I can do to avoid further problems inside the lens due to humidity it might have entered? (fungus... etc)

Thanks a lot for any direction or comment

bump ... nobody had issues with the zoom lock?
Tks.

Wow, havent heard of this one before. First and foremost: YES you should and CAN send it to Canon. Is it by chance still under warranty?

Unfortunately warranty ended 2 months ago... I was hoping someone can tell me the cost of the repair or if it is something "common"...
The major issue is that the zoom won't stay in the 100 position when is resting vertically