Here is a UMI X1S Stock ROM Firmware which can be used to load and flash stock firmware on any UMI X1S of this exact variant. Any MTK Flash tools can download and flash this UMI X1S flash file on your X1S so long as that MTK Flash Tool supports MTK Scatter File.
Since most major software malfunctions on any MTK Android devices can only be corrected by flashing, this X1S flash file, if properly used, can unbrick (debrick) your X1S and also corrects any software issues your UMI X1S may currently have. Also, keep in mind that when you load stock firmware on your UMI X1S using any MTK flash tool, your UMI X1S will be reset to factory defaults settings and by that, definately, your UserData will be lost including contacts, messages and others.
Note: If your X1S is already bricked and you want to unbrick it, you will need to pay closer attention to the tutorials contained below here.
UMI X1S Stock ROM Firmware Download Link(s)
1. UMI X1S_20130628_PC Stock Firmware Download Link
How to Flash Stock Firmware On UMI X1S
1. Download your UMI X1S stock ROM firmware from the link above.
2. Extract the UMI X1S Firmware you downloaded from the link above onto a folder on your PC.
3. Download and install MTK android device drivers on your PC. You may skip this step if you have installed MTK drivers on your PC already otherwise, download MTK drivers here
4. Now, choose either of the tools listed below here to load the stock firmware on your UMI X1S.
2. NCK Box
3. Miracle Box
See video tutorial here: How to Flash MTK Android Devices Video Tutorial
Note
1. Each of the tools listed above contained step by step guides with illustrated pictures on how to flash stock firmware on your UMI X1S.
2. If your device is bricked already, I recommend that you use NCK Box or SP Flash. Both are the safest toolS for flashing MTK Android devices.
3. If you require any further assistance, simply drop your comment detailing the issue(s) and I shall help you revive your UMI X1S, if need be.