Thanks for the share and that is great news for you.
All the Gurus on here would recommend against it, but the good thing is, it worked for you.
I agree with you on the Proxmark front, and I have said it before, Great device, Just Not user friendly.
Here is my regurgitated info on the White cloner that may come in use for you shortly.
Or not “If It Aint, Broke don’t fix it” 
NOW this is all supposition, but maybe now because of your White Cloner and how it writes, your xEM may now be “protected” from your work access system trying to write to it???
Also, again I could be talking out of my Arse 
here, But with a ProxMark, by setting a password, you again may be able to protect work access system trying to write to it???
There is, I believe, still in the works, is a Dangerous Things Reader / Writer. That will be much more affordable and easy to use… speaking of easy…let me get back to you shortly. I will update this post…
FOUND IT
@Emumanx ( Kent UK ) made a post about the Cheaper Proxmark Easy ( 100 x better option than your White cloner ), here is a link to his post, seller name, price ( significantly cheaper than PMIII ) and obviously the original thread about the easy.
The downside is, it is not compatiable with the DT / Tom Harkness LF antenna, but people are still getting successful read / writes with the Easy.
I am not sure of the DT reader writer time line but 
Might be time for another xEM or a NExT, One for your current systems, and one to experiment with!?