I sent you a DM so we can check a couple of thingsThere is an old issue that has returned on this phone. The Firmware is exceeding the available space on the phone to perform the upgrade. This was a problem a few years back that bricked a LOT of phones. Looks like someone did not do the testing before release again (Yealink, not 3CX).
I do not recommend pushing this update. You run a chance of bricking the phone. If you DO NOT need the router capabilities, then leave it alone.
Please 3CX, was is the best course of action here?
This does not apply in your case - you need to find their support resources and upgrade your phones to V86 first.There are detailed instructions on the Yealink website specifically for 3CX:
https://www.yealink.com/en/solution-detail/resource-for-3cx
Founded in 2005, when VoIP was an emerging technology, 3CX has gone on to establish itself as a global leader in business communications.