what is your suggest while do repair it . it has failed 2 times . 2nd time overhaul complete engine with new short block / bank 1 cylinder head with OEM valves / recall valve springs / rockers / lashes / new cam / new timing gears . but unfortunately again within 2 days bank 1 rocker fallen ..

Having too much lash clearence would allow the rocker to move around. I know that papadakisracing.com had a problem with the toyota 2ar, about the same rocker setup except we have lash caps for shims that sit on the valve stem.
Start at 5:00 for valve train.

https://youtu.be/7PVc7pKzF64

I had considered that, but i'd imagine they would have to be quite a ways out of spec. I had a couple that were on the lose side of spec, but not out of spec. My experience with bucket shim setups from motorcycles always seemed to be that they tightened as they wore in. So I let them be.

In the video you will notice that the exhaust has the shaft rockers. I would assume it happens more on the exhaust so maybe heat.
Their is also another video that shows how he redisned the rockers with deeper grooves when he was having problems.
One theory.
If the lash is loose the lifter could leave its seat and fill with oil and then when the cam hits the rocker it slams the lifter down creating oil pressure that pushes the rocker off the pivot