This is Allen from DUON System.
We investigate to figure out the cause for this issue during 3days, but we couldn’t get any problem. The unit is working very well, and also the parameter is configurable with 0 after zero trim.
Please note we conclude that this unit has no problem, it would be better to check field condition or the other external factors. Although there is additional cost to investigate in our factory, in this case we will do for free of charge.
Please get this unit back to your office, and shipping cost will be on your side.
Or if you can inform any account for your carrier service, we will dispatch shortly.