its been my experience that when a ice machine is given away..its not any good..that said, ice on the bottom of a evap in my opinion is from a lack of freon..
did you pressure test the system?? if not , theres a tag on the machine that has the high and low psi requirments..psi it with dry nitrogen to the max of the low psi reading on the tag..then do a sniff test..and use the blue leak test soap as well..i have a high dollar GE leak detector, and it went right by a leak..but the blue soap found it..