TNY275 start up problem

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In our last production batch we had 20% malfunctions. We investigated that BP/M pin (connected to a 10uF-X5R ceramic) keeps 0 V. After changing the 10uF to a 100nF ceramic - it works. Also if we change it to a 10uF Alu Elko - it works. Sometimes if we change the original 10uF back then it works again.
What happens inside the switch controller? Could it be that the tolerances of ESR (D.F. <=12.5%) of the 10uF ceramic is sometimes too low and the regulator within the TNY275 shuts down? Is there any restrictions in the use of the BP/M pin capacitor?
Has anyone an ideas? You would help me a lot.

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schematic+pcb.pdf1.89 MB