"Contact" is uncountable in this context,, so you need the singular form and "is", and you probably need "between" rather than "of", but it seems to be an odd thing to say. It is difficult to imagine any machine where there is not contact between its moving parts, such as shafts rotating within bearings or one gear driving another. However, even if you change it to say something like "unwanted contact", how is the person meant to check for this or to know when this happens?I see.
So you think it would be ok to write it:
"If contacts of moving parts in the machine are detected, make sure to turn off the machine."