This seems like a bug in the CRM. 

Luckily a sales rep alerted us to it very quickly. Basically a workflow rule that was set up to trigger on creation of a client meeting (with no conditions) suddenly stopped working for the last 5 meetings created. 

We were able to reproduce this bug initially. Turning the workflow rule off and then back on fixed it, but it's extremely worrying that this happened in the first place!!

I tried opening the workflow rule to debug it further but I was again met with errors. I got this when i tried to edit the function that the workflow rule should trigger:

Wondering if this is just us, or if anyone else is experiencing this too.