Unexplained Depreciation Adjustment passed by system when Depreciation Method is changed

We have changed Depreciation Method for an asset.

Both methods are almost same with same rate and type (Reducing Balance). The only difference is Depriciable Basis (changed from Period End to Year End Balance)

In the period of change there is an unexplained depreciation adjustment passed by system. We do expect an adjustment but it should be a very small amount because rate is same. But this is a big amount.