Tablet crashes after battery replacement

SM-T520 10.1 wifi, purchased summer 2014, January 2017 replaced the original battery as it was "dead" - everything works fine except that the tablet crashes (over and over again) as if the battery were physically disconnected. Tablet will not boot (power on), always need to plug in the charger and when it shows charging progress, it can be turned on - but the tablet date and time are "set back" to original/factory setting. All apps etc are there, hence the crash doesn't cause a real "factory reset", only the previously set date and time are "gone".

Disconnecting the battery and re-connecting done, factory reset performed, crashing issue persists. It is very unlikely that it is caused by a "loose/bad" contact of the battery cables or any other connectors etc...

Any idea how to check/verify the root cause and to repair it?

Thanks

Boris