Don't worry this isn't the machine I just rebuilt last year. Today me and my Dad removed a Frigidaire Gallery Front Load washer under the Kenmore name from a friend's rental property. We swapped in a donor spider that was still in great shape 5 years ago and now the issue has reoccured after just 5 years of use. I dismantled the machine today and I found the shock absorbers were still very stiff so I kept those, Upon splitting the tub, I noticed the arms of the spider arm were not very corroded and instead the entire middle of the spider was rotted, The center of the spider wasn't just broken. IT WAS GONE! With the drum being somewhat clean and not covered in gunk, I can only assume this poor machine never or rarely saw hot water, The door was never left open between uses as this poor machine was stuffed inside a closet with a 24" Asko Dryer on top of it. Being a rental property, I can almost bet that this machine was abused. Now it doesn't make any sense to me how a machine at a rental property with light to medium use broke 2 spider arms when mine saw heavy use and the spider looked almost new. The Spider arm in the last picture is the one from my Frigidaire Gallery when I disassembled it to replace the bearings. I could tell that my Frigidaire Gallery endured heavy use because the shocks were shot and the dryer's start switch was broken. Of course with this poor machine at the rental, I feel like it was abused like I just said. It just doesn't make sense to me that a lightly used machine went through 2 spider arms when my machine is on it's original.
To me that says volumes about poor laundry habits and correct proper use. Your machine may have been abused but it was evidently used with hot water and correct detergent and allowed to dry between uses. Personally have never encountered any issues as always hot wash every week with quality powder.
I was reading about the causes recently, apparently it is usually caused by crevice corrosion.
The spider gets coated with a layer of biofilm, detergent residue, lint and other grime as a result of poor laundry habits.
The film traps moisture.
Some types of bacteria can cause pitting, thus penetrating the aluminium oxide passivation layer.
The film results in a reduction of dissolved oxygen which varies across the surface, and the differences in oxygen concentrations can result in a flow of current, with the areas of lower concentration being anodes (oxygen concentration cells).
If chloride ions are present they will result in the formation of an acid at the anode, accelerating the corrosion. The lack of oxygen and also chloride irons, inhibit the reforming of a passivation layer.
(Lincoln UK) 
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