Looking for a explanation/cause of lithium polymer battery failure
There might be some interesting oscillation going on between the MCP73837 and the DW01;

If the MCP73837 triggers (Vbat > VOCP) the DW01 in either "FAST CHARGE MODE" or "CONSTANT VOLTAGE MODE", the battery will 'disconnect' and the parallel capacitor will fully charge and put the MCP73837 in "CHARGE COMPLETE MODE".

The MCP73837 goes back into "FAST CHARGE MODE" if the voltage drops below some threshold (Vbat &lt; Vrth).

That will happen eventually because the capacitor will lose charge... however before it reaches that point it is possible that the DW01 resets (Vbat &lt; VOCR) and the battery is 'connected' again.

Should the DW01 reset around the same time that MCP73837 goes into "FAST CHARGE MODE"
it is conceivable that the battery might be stuck in a loop that repeatedly charges the battery in "FAST CHARGE MODE" -> overcharge protection -> "CHARGE COMPLETE MODE" -> etc.

You could try removing the DW01 from a couple of fresh batteries and see if the problem persists with charging. If it stops you know the two ICs aren't playing along nicely.