I am using OrCAD PCB Designer Professional 17.4-2019 S002 [1/6/2020] Windows SPB 64-bit Edition. When I try to refresh a symbol, I get the following warning:  

WARNING(SPMHA1-127): Illegal subclass. Occurred during saving the design.

Is the symbol or design layer corrupt?  To work around this issue, I have been removing and re-placing symbols instead of updating them. This however, is very time consuming and not efficient use of my time.  



First, download the latest hotfix for Cadence for 17.4. The s002 hotfix you have installed is older and there have been fixes made since that release. 

Secondly, run Check > Database Check on the board file to see if it reports and corrects any problems.

If DBDoctor reports but fails to fix the errors you will need to send the board file to us to see if we are able to correct the problem for you.