Hi,
I just did a search for "reset" in the datasheet.
* there neither is a reset pin
* nor a reset function.
Please explain what really happens.
***
The only function I see is "set to midpoint at power up".
If you expect this to happen, then you need to verify this. How exactly do you know it is set to "midpoint"? You have to exclude that it is any other value than "midpoint", else you (and we) are focussed in the wrong direction.
If really "midpoint" then (as long as you treat the device according datasheet specification) the only reason is a failure in power supply of the IC.
(In opposite to this IC a microcontroller may have a several sources for RESET, like power supply, software reset, external reset, watchdog reset, ...)
***
But I'm with the others: I think the root problem is a schematic or PCB layout issue.
Klaus