After I click "done" after reviewing an online PDF in the commenting interface, here's what I got in all red (screenshot attached, too):

Encountered an Unexpected Error
TypeError: Cannot read property 'routerpath' of undefined
S (https://documentcloud.adobe.com/dc-web-app-dropin/1.10.11.27.0/bootstrap.js:1:51750)
Mn (https://documentcloud.adobe.com/dc-core/1.10.1/dc-core.js:1:45536)
$n (https://documentcloud.adobe.com/dc-core/1.10.1/dc-core.js:1:57677)
Yn (https://documentcloud.adobe.com/dc-core/1.10.1/dc-core.js:1:57985)
fr (https://documentcloud.adobe.com/dc-core/1.10.1/dc-core.js:1:61367)
sr (https://documentcloud.adobe.com/dc-core/1.10.1/dc-core.js:1:60876)
ur (https://documentcloud.adobe.com/dc-core/1.10.1/dc-core.js:1:60702)
or (https://documentcloud.adobe.com/dc-core/1.10.1/dc-core.js:1:60074)
Zn (https://documentcloud.adobe.com/dc-core/1.10.1/dc-core.js:1:59433)
Object.enqueueSetState (https://documentcloud.adobe.com/dc-core/1.10.1/dc-core.js:9:22789)
FocusRegion.o.setState (https://documentcloud.adobe.com/dc-core/1.10.1/dc-core.js:40:796)
https://documentcloud.adobe.com/dc-web-app-dropin/1.10.1_1.27.0/bootstrap.js:1:70230