I have some background in electronics and analyzing those intermittent failures that these miners have just got me a little confused, specially during a time that I checked control boards and data cables by disconnecting back and forth. At times the miner was full throttle mining just to drop after few hours. That in electronics is called a "cold soldering". Although there are not visible cold solderings I discovered that the soldering material that is being used on this S17 have 2 problems.
First, high amount of lead and low proportion of tin, and of course zero silver in the soldering material. This can be observed under the microscope used to soldering circuit boards. All of the solderings showed a greyish mate color and no shinning finish.
Just to let you know, the greyish finish comes basicly from lead free solder. All Manufactors are forced to use leadfree from 1996 on for consumer products. You may test it using a handheld analyzer (in production used to check material prior production).
That you expirience cold joints is a old problem also on S5 and S3. To repair that, I use no clean flux paste around the affected chip then a heatplate on the underside of the board (regulatet to 100° c) and warm the pcb up for arround 3 min. before I am using a regulated hotair (360°c) on top to melt the joint and reestablish connection. 99% this method works. 1% the chip was realy dead before that action.
In conclusion I can say that bitmain did not got their reflow process in control, and no qa off corse.