I’d say that there absolutely is a more reliable reader/writer for the xEM in my experience. I purchased this slightly more expensive device which has a display and actually shows the format of the card you are copying visually, and gives you direct confirmation of read and write successes. It lights up the xLED like crazy and writes to my xEM with zero issues. The only issue with it is that it also password write protects your implant/tags after writing to them, however it is a known password. If you were ever to write to it using something like a proxmark3 you’d have to input that password, but if you just continued to use that same writer you would never even know it had been password protected in the first place. The one I have is the “White Multifrequency Cloner” shown in this thread, which has a tonne of great info for this.
If you’d like a link to where I bought mine let me know, as there are models of varying quality, but if you search on Aliexpress or Amazon and read the review you should be able to find it no problem.