IT might be a good idea to have a local tech or several if you can find them, you can trust go over this radio. The more inputs from various opinions - helps you make a better choice whether to keep or let it go back to the family member of this radio.
It's similar to the Stryker 497 - and similar in Galaxy design (more than you know)
So, to me, when you "chat" and then it starts to "cut out" like that - might indicate overheating - not caused by just using it, it's not designed to do this. So, when things shut off like that may indicate some more serious problems may underlie a condition of age or previous abuse the family member may not have been aware of.
So once it started acting like this - if I depended on this device like I do a car to take me back and forth to work - treat it as a repair issue - you might need some people to look at it to give you several opinions - so you can get a better idea as to what course of action you can or should take.
We can't do much for you like this - but we can advise you to find some people you can trust to help guide you and be careful with those around you - you have a radio that many would want for their own and potentially take advantage of situations like this - guard your heart so you don't get taken - so you don't get more damage done to the radio, if by then that happens, then it's no good to anyone after that event.