Mom's KDS17A did the same thing many moons ago.  The spindle the wash arm rotates on had come loose and risen up to the point the wash arm was hitting under the bottom rack track and getting stuck.  I pulled the spindle out, wrapped some teflon tape around it several times and then twisted it back down in there.  It never came loose again and worked fine until the motor died.  I'm sure there was/is a better way to fix it but there was no internet back then (early 1980's) and I just improvised.  As is stated above...a picture is worth a thousand words.

I don't know what your wash arm support looks like but for many years they were very similar.  Based on Stevet's recommendation I used some Marine Epoxy to temporarily repair the issues with my support.  I used the popsicle sticks to hold it in place until the glue dried.  This worked brilliantly.

I had to glue the spindle in place as well as close up some cracks.  I was lucky to find a new one on eBay but I used the repaired one for two months or so.