Help This thing dies when disconnecting from charging.

I have just bought a fenix 5. Desperately disappointed, when disconnecting from charging the unit shuts off and won't restart. When you reconnect it sometimes registers 0% battery and charges again or sometimes 100%. It only works after disconnecting maybe one in three times. Battery life on those occasions is less than 12 hours. If you try and do an activity the longest has been 10 minutes or so. Its very close to going through the bloody window, help please anybody...