I'll have to agree with way too much 134a in the system. Like stated above, find some one with a recovery system and remove the 134a, and reinstall the correct amount. As far as the oil goes, normally there is too much oil in the systems. If oil was added to a system that had oil in it already the system may have to be flushed to remove some of the oil. Also too much oil will not pass through the Expansion valve (or block), and cause a blockage of oil in the system or too much oil in the compressor will not compress.
I havn't heard about the propane in the R12 or 134. Some of the blends have a form of explosive chemical make up in them, like propane. Usually was happens with these blends is that they seperate, when some of them seperate the molicules are small enough to leak out of the pores in the AC hoses. Usually the remaining compound is explosive. This problem has not been as big in systems that were designed to run 134a, as they have barriar type hose, to retain the smaller molecules of the 134a. The older R12 hoses tended to very slowly leak the smaller molecules. (Propane is a great refigerant... just one down fall... BOOM!!!!)
Here in TX the purchase of 134a is over the counter with no license. R12 requires that you have a special license to purchase the product.
I hope this help. .
Bryan