Hi I totally forgot to pack the magnetic portion of the smart sense sensor when I moved.
The smart portion still works of course as a vibration and temp sensor.
I bought a universal alarm contact sensor but that doesn’t consistently work (actually it only infrequently works) can anyone recommend me a contact sensor that will work?
I could be wrong, but in most similar sensors the piece you left behind is only a magnet in a plastic case. No radio, no sensor: those are inside the body that you did bring. So try any inexpensive bar magnet and it may work just The same as it did before… 
that’s correct that’s all it should be
this is the one I purchased from amazon but they are flakey at best:
https://www.amazon.com/gp/product/B01M8JCGSO/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1
I’m confused. Why not just get a magnet to replace the piece you left behind? Why get a whole new sensor?
https://www.amazon.com/30-Pack-15-6-5-Rectangular-Magnets/dp/B077BWCC8D/
I bought that kit from amazon just for the magnetic section to use with the sensor, it was cheapest and fastest solution possible.
Then i’m still confused: there’s nothing about a magnet that can be “flaky“ unless it’s too weak to draw across the space where you have it installed.
your guess is as good as mine. it works with my genuine SmartThings magnet on my other door sensor