I am having an issue with oil migration in a R-508B cascade system,(POE Oil) I have several units on site and have never had an issue until now. Different manufacturer! I have seen others suggesting pentane or oil control units, however I would like to know if anyone has experienced this issue and resolved it with one of these products? I have some reservations regarding use of the pentane although I used it on another unit based on manufacturer recomendation, this was a R-13 mineral oil application.