You can start a sentence with 'among', but it doesn't work in your sentence. Among is used for countable things, and 'equipment' isn't countable.
'on' isn't a good option. Try 'about', 'regarding' or possibly 'for'.
You have used 'stops' with plural 'controls', which is incorrect.
It's probably more natural to use a superlative with 'Among'.
Among our different items of security equipment, we most often get requests about remote controls that stop working.