I have had this conversation numerous times with Shopify. I have switched over to Shopify POS 4 months ago and am still having this issue.
Shopify has told me that they updated the app and now it is fixed. NOT TRUE. It is not fixed nothing is fixed.
They then told me my TWO scanners are broken and my TWO card readers are broken. Is that even possible?
We have figured out ways to make it work once in awhile, but this is completely unacceptable to the point that I'm going to close down my website and go back to my old Quickbooks POS. Quickbooks is not the best but at least they don't have excuses and cause me to wait 3 hours every time something disconnects.
TO SHOPIFY - Fix this or find yourself a new customer.