Hello, I have been reading every single answer to this interesting post. This is because I have also been framed by Bitmain with those S17+ antminers. 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.
 
Second, below normal temperature of the soldering material, also leaves traces, specially on the hashing board chips. Also analyzed under the microscope there are traces that look like an sponge along with tiny cracks surrounding the chip's area at the surface of the hashing board.

So, this takes me into the conclusion that somebody at Bitmain's is trying to cut ends and by doing this they have compromised 50% of the S17, T17 series. The use of soldering with high percentage of plumb just tells me that they are throwing the cheapest crap they have to solder the components on those miners. Also they are trying to reduce electricity costs by not heating well enough the soldering material melted at the trays and this is specially true because the soldering material with higher proportion-ratio of lead instead of tin and silver takes colder temperatures to melt.

So taking all this into consideration I really recommend to all of those that are willing to throw the money into shipping costs, customs fees and no mining income, just don't do it because Bitmain still uses the same bad quality materials to fix it.

Since that soldering material is all over the hashing and controller boards is just a matter of time chips keep coming off the boards, the only and costly solution is to desoldering them all and soldering back with a good quality soldering flux, other than that those miners will keep failing over and over.

Basically most of the S17 series are doomed.