To increase the success rate, the following points should be checked and noted:

1). First of all use ONLY FLEX power supply. 

2). If cannot glitch, test your Flex by cleaning the I/O connection (connection between Flex and Flexbox) and glitching worked.  If nothing is working, check your Flex!

3) Use as short cables as possible. Too long boot wires will fail the procedure. You need to make shorter cables it’s always was like that in any boot or jtag connection – to long cables interrupt to glitching process.

4). If fails many times with the Flex FLX4.1 cable, solder directly with short wires.

Try without FLX4.1 and connect directly to the E port.

Check and change wiring for E port. Check the resistance of your wiring. The boot pin also looks very thick! It may not be making good contact, or the boot pad could already be completely gone.

5). Bridge resistor gap with solder and remove the resistor (0.1 ohm).

6). Reinstall flex software and use a different WiFi (One of Flex users had issues with flex. It’s killing the internet; use different WiFi it works).

Also swap out to different power and ground leads, these are known to break near the ends, this protocol draws a lot of current so a weak cable could cause issues.

7). Call MMS support.