We are using Dojo version 1.10.0 for our product. DropDown button is working fine with Mozilla version(56.0) but it is not working with Mozilla version(60.6.1 esr ).
For reference I attach an screenshot of Mozilla version(60.6.1 esr ).
i don’t know much about dojo yet, as i’m just getting started, but could you maybe use the debugger to see what line of code the error points to?
As i find the code of dojo is written very clearly it might be quite easy to address the issue.
Or is it just a displaying “thing”?
Screenshot is a bit confusing for me.
I’m trying to help you out once i really understand your problem 
And maybe set up an example page where i or anybody else could try out the code?
Didn’t recognize it was 5 months ago. lol