There is a lot going on in the code for events like join and nick, so providing details on what it does would be difficult. If you are trying to manipulate the nick list in the same event as the nick list is being updated, it may simply be a timing issue. If you delay your own processing with a /timer until after the event has been processed, does it work then? If not, we would need to see a minimum script example, that is as small as possible, that reproduces the issue.
