I've noticed this over the past 3 weeks - that while the majority of registered users are being logged by the com_profiler plugin with logins and logouts, there are a few who randomly get logged, but other times do not. Comparing the logging between the com_profiler and the k2 plugin shows that users are NOT showing up as being logged 'in' by com_profiler, but are definitely logging in to Joomla because they are logged by the k2 plugin.

Right now there aren't ANY restrictions on IPs, user_ids, etc. that would be interfering with the logging, nor is the main plugin restricting logging to registered users.

I can't find any commonality between the users who haven't been logged correctly - there is nothing special about their system user ids, nor the time of day this is happening.

I'm beginning to think that the com_profiler plugin has some issues.