I had a similiar issue eseelke. What was happening on my end is that the devices I uninstalled from customers cancelling previously was interfering with current customers and causing syncing issues with repair shoppr. What you need to do is create an inactive account Customer on Kabuto and transfer all of the uninstall devices to this account.
In order to do this you need to go to devices and have it show only uninstalled devices. Then from there you need to select them all and transfer them to the Inactive Account Customer that you created earlier. To do this you need to click on the button that looks like an equals sign = but with arrows pointing opposite directions.
This should fix the confusion repair shoppr is having with the Kabuto devices that are synced with it.
For some odd reason when uninstalling devices from a customer it doesn't fully remove that device from said customer and causes issues later in Repair Shopper with syncing. Also we had issues where uninstalled devices that did not have a customer assigned to them were randomly selecting a customer and attaching them selves to a random customer.
I am not sure if this is an issue that can be fixed, but that is the work around we are using to resolve the syncing issues between Kabuto and Repair Shoppr. Once we did this all of the devices in Kabuto synced up right away and all the issues with customers not being build correctly we were having resolved itself.
Kinda of a long winded explanation, but I hope this helps!