Yes, I will be outdoors (in my vehicle) when the dropped calls are made. My signal appears to be fine when outdoors/in my vehicle and often carries 4G LTE without issue.
I have apple's silicone case on the device (a very minimal case in comparison to something from Otter for example). I have not noticed any issues with my signal with the case on or off.
I followed the troubleshooting guide on verizon's website and found that disabling and re-enabling HD Voice appears to have improved my situation for the last 2-3 working days. Any other advice is welcome.