Anyone see differences in Workflow rule behavior between Classic and Lightning?

I have a workflow rule that evaluates some fields for changes using the PRIORVALUE function.

The workflow rule has been in production for one group still using Classic only and it works just fine.  I wanted to use the same rule for a new group that will be using Lightning only but found that the rule fires when it should not (values are not changed) but only under Lighning UI.   If I switch to classic UI and make edits to the same record (but tested values are not changed) the workflow rule does not fire (expected behavior). 

Here is the formula for my workflow rule which is set to fire anytime record edited (only option if using PRIORVALUE).  Goal is to determine if the user has increased the opportunity discount and if so set a flag that the user must get approval again.

PRIORVALUE(Discount_Approved__c) && 

Discount__c > 0.0 &&

RecordType.Name = "Lift Sales" &&

   (PRIORVALUE(Discount__c) < Discount__c ||

   PRIORVALUE( Discount_Amount__c ) < Discount_Amount__c )