@Scott_R, I appreciate your help here on what you've done to have your concern rectified.
@Csoule, I wanted to ensure that everything was covered here. How's it going with your thermostat? Have you had a chance to reach out to an HVAC technician for consultation? I also found an article that might help about the Common Wire. Please let us know if you have any other questions or concerns.
Nest/Google seems to blame the common wire for every problem. Nest battery failing? It's the common wire. Unit not turning off? Common wire. House on fire? Common wire.
When I was trying to figure out the issue with the blower staying on, Nest support insisted it was the c-wire. They set me up with an appointment with one of their pros to come and do the install. The "pro" did some weird reconfiguration of the wires, which didn't fix anything but actually started making things work even more strangely. I got my HVAC people over; they replaced the stuck relay on the blower (the actual problem) and fixed the mess the Nest/Google -referred "pro" made of the wiring.
Still not dispositive, but I had a similar issue with the relay; physically shutting the power off at the air handler fixed things for a bit, but it started getting stuck on again. Control relays are electromagnetic--physical as much as electronic, so can literally get stuck.
Since you said it was still heating even with the Nest pulled, in my limited experience that made me think the issue was with the heating unit and not the Nest itself.
Thank you Scott...I have 5 units/air-handlers and 5 nests tstats on my second floor for each bedroom...my HVAC person who installed them could not get them to work right with the Nest...he had originally installed square white ones...can't recall the brand right now, but they stood out like a sore thumb. I have an old historic home, and the nest is not as intrusive. I have unico system on the 1st floor with 3 nests and that system is working including steam heat from a gas boiler as my main source of heat. Lends me to think what your saying is correct because I have not had problems with those 3...the problems are with the 5 LG units. However my 1st problem I had was the hvac person did have them wired correctly (only blowing cold even when in heat mode and nest on off) and I got that info/fixed through this site, once I changed the white wire it was good...but then this happened... Thanks Scott, you probably hit the nail on the head! I appreciate your insight, this has been frustrating especially since my hvac "specialist" and the LG rep could not figure it out! Honestly they were negative abt the nest from the beginning and even though they spent HOURS trying to fix the issues I really think they wanted me to give up on the nest. thanks again!