Hello Scheduler Experts!

I've been struggling with an issue for 6 months now and was hoping for a fix, to no avail. Here is some background of the issue and the support issue. The net is that jobs are running way too frequently, resulting in performance degradation, database bloat, etc.

As I continue to see if I can help identify the source of the issue to present to the DNN guys, I noticed the following today. There are several pieces of information here that either I am mis-interpreting or just don't jive. 

For example:

1. Status = Waiting for open thread, even though the Free Threads is 1 and Active Threads is 0
2. Max Threads is 1, yet most jobs listed have a different thread number. Some have -1, which I don't know what that means. But if max threads is only 1, not sure why each job would be queued to run in a separate thread. Is this irrelevant anyway? By that I mean even though the jobs are queued in multiple thread ID's, is there a gatekeeper that will still insure only one thread runs at a time (since max threads is set to 1)?

It seems that if I have a job that is scheduled to run at wide time distances apart, i.e. every 1 day, there is no issue, but if I have it set to run every 15 minutes, I get instances of the job running multiple threads at once or within seconds after the last, resulting in that job running 15 to 20 times within a minute instead of just once every 15 min. (You can see examples of this data in the above "background" link, and its not just my custom job, but other core jobs doing the same thing)

I want to use the scheduler to check for the status of some data and if certain thresholds are met, to send an email alert to my users. But I can't risk it sending out the same email hundreds of times a day. Is anyone else using the scheduler to send emails and having this issue? Or in general seeing jobs running more frequently than specified?

I too am having the same issue and have been trying to "fix" it for about a year as it was causing MAJOR production issues.. I have done everything that Mitch Sellers recommended as well, Timer Method, etc... nothing worked.. ended up creating my own process and now run it just using plain old Window Scheduled Tasks... the scheduler bundled with DNN is not reliable and I find it hard to believe this is not a hotter issue for DNN to fix as this issue has been around for a long time...