How to troubleshoot Scheduled Reminders

Question

A bit of background: I have several scheduled reminders triggered by activity types, which started to work unexpectedly after installing the CiviRules extensions. Once the extension is installed and enabled, after a scheduled reminder is triggered, it sends the message every time the cron job runs (every minute, as the activities are created on form submission from the frontend) and on top of that it doesn't log any activities to the targeted contact. Checking the job log I get this:

Parameters parsed (and passed to API method): 
a:1:{s:7:"version";i:3;}

Full message: 
Finished execution of Send Scheduled Reminders with result: 
Failure, Error message: API (ActionLog, get) does not exist (join the API team and implement it!)

This was reported twice already, here and here, there was also a open issue, see CRM-17128, which was marked as closed, Cannot Reproduce, for obvious reasons if the issue has to do with CiviRules, which I believe it is, I've tested it on a fresh and clean install with CiviCRM 4.6.4/4.6.8/4.6.10 and Wordpress 4.3.1 and I can confirm that the issues only appears after installing/enabling CiviRules and it reverts back after uninstalling it. I've opened an issue in the CiviRules github project and I'm waiting for a reply but menawhile, my question:

Where to start debugging scheduled reminders?

Any help would be appreciated.

PS: no errors in Civi logs (debug and backtrace enabled) and no errors neither in apache/mysql logs.

Answer 1

Thanks to @jaapjansma from CiviCoop for all his help and support. The issue has now been solved and merged into the main CiviRules development, if anyone is facing this issue, check out the fix and PR here.

As an answer (kind of) to the question:

I couldn't find a straightforward way to debug so, in this case the Reminder Sent or Membership Reminder sent activity that Civi creates when a Schedule reminder is triggered wasn't created, that was the lead to investigate, using CiviCRM's debugging documentation (in a test environment, of course), turned out that the activity was created but with improper values, therefore the Schedule Reminder cron job would keep sending messages until the activity was completed.

Posting this as an answer just for the record.