My experience here might be somewhat unique because most people I know go through a batch so quickly that they would never make a connection between a side effect and the pot. In my case I use very small amounts on a regular basis usually a few times a week and a small batch might last me for a year or more. This gives me plenty of time to identify a side effect and verify it.
The most serious side effect I had was a severe case of arrhythmia where my heart would roll over in my chest every 3 rd beat. It would subside almost exactly 72 hours after my last hit. The most common side effects I experienced were small cluster headaches that were isolated to a very small part of my head, A pretty severe facial twitch that affected the entire left side of my face was another one. Most of these symptoms will usually subside in 3 or 4 days sometimes less. The last several months I have been experiencing severe intestinal cramping, it just occurred to me today that this might be a side effect so I am quitting for a while to see if they subside.
I haven’t purchased anything new for several years but sometimes a buddy will give me a sample and I just mix it in with the batch I already have. I will post back if I notice any difference or not.