"The resource you are looking for is not available" - adding items

I recently updated to version 8 and restored all of my data from the version 7 website. Now, whenever I add an item to a quotation or sales order I get the error: “The resource you are looking for is not available” which comes up twice, which makes me think it’s calling some unknown method twice. This error did not occur in Version 7 and I’m having trouble locating where this might be happening/what might be causing it. Any guidance would be appreciated!!

And this is the error I’m getting in the console:
Unable to handle success response
TypeError: Cannot read property ‘length’ of undefined
at eval (eval at frappe.template.compile (desk.min.js:2562), :5:27)
at Object.frappe.render (desk.min.js:2576)
at Object.frappe.render_template (desk.min.js:2587)
at Object.callback (erpnext_controllers.js:292)
at Object.callback [as success_callback] (desk.min.js:1385)
at _ (desk.min.js:1409)
at Object. (desk.min.js:1506)
at i (jquery.min.js:2)
at Object.fireWith [as resolveWith] (jquery.min.js:2)
at z (jquery.min.js:4)
at XMLHttpRequest. (jquery.min.js:4)
(anonymous) @ desk.min.js:1510
i @ jquery.min.js:2
fireWith @ jquery.min.js:2
z @ jquery.min.js:4
(anonymous) @ jquery.min.js:4

From the browser’s console Network tab, you can check which function it is calling. That might give you some idea. Also check the permissions once.

Same. I am having the same issue and can not seem to find any solution.

Solved my issue:
In one of my custom modules, I was trying to import something that existed in Version 7 but not in Version 8.