Issues with migrating mbox.js to at.js

We started our migration from mbox.js to at.js and as first step we loaded the at.js through adobe target configuration which worked well. After loading the at.js in the page, we are receiving the following error

Uncaught ReferenceError: mboxFactoryDefault is not defined
at aam_tnt_cb (analytics_min.js:formatted:7031)
at event?d_stuff=1&d_dst=1&d_rtbd=json&d_cts=1&d_cb=aam_tnt_cb&d_dpid=604:1

From our understanding, mboxFactoryDefault is deprecated and not used in at.js.

In our analytics_min.js mboxFactoryDefault.getUrlBuilder() and other methods are throw errors.

Is there any way to replace the mboxFactoryDefault or other mboxFactoryDefault related methods with ones used in at.js.
Please help.