I have been using Mokee ROM on my ZTE Nubia Z9 mini for last six months. I got started with Android lollipop 5.1 ROM and soon moved to Marshmallow, while the stock ROM is stuck on 5.0.2. Generally this is the case with chinese OEM's but the phone is solid with more than one day of battery life, great camera and overall snappy response.
Anyway few weeks back I started seeing this file moving/ copying issue where the inbuilt file manager won't copy the files correctly. When I copied more than 1GB of files then it would fail to copy 1-2 files to memory card. This was infuriating.
I thought maybe it's the apps problem and tried ES file explorer. But with ES file explorer also I got similar issue. After using ES File explorer for about a month and noticing this issue a number of times, I decided to use some other file manager. Because this is a basic function and if a file manager is failing in this then there's some serious problem with the app.
So last week I stumbled upon ZenUI's File Manager which is Asus file manager app for their Zenphone's. And I have been using it for one week and everything's working fine. The application interface is great, the copy/ move workflow is well thought. E.g. with Mokee's own file manager, you select a number of files and then you move to target folder and from a hamburger menu there, you select "Move Selection here..." which is un-intuitive in my thoughts. In Asus File Manager, you have a "Move to" option in hamburger menu at top right corner. This opens a dialog box where you select a target. It shows last four folders as well and this helps a lot. After you select move, and tap OK, move operation launches. After moving is finished, you stay in your original folder only, which means you can move some more files to other folders quickly.
This is great!!
Another feature I like most from Asus ZenUI File Manager is Storage Analyzer which is faster than ES File Explorer's analyzer and quickly shows you the files eating your precious storage. Overall I'm very happy with Asus's File Manager.