I don't know of anyway of 'downgrading' a PRPC installation to a lower version: but you *might* get away with exporting your Application (via 'RAP' etc.) from 72 and importing into a 719 - I haven't tried this (only ever done this other way round) - but it might work if you have not used any 72 specific features that didn't exist in 719 in your application..... (You will probably need to adjust 'built-on' versions in your ruleset/application stack as well...)
I went ahead and imported the application that was built on Pega 7.2 over to Pega 7.1.9.
The import had errors - which was expected. After the final step, 16 records were skipped and 156 errors were reported.
But went ahead with it. I get the below exception when I try to launch the manager portal. I have attached the screen shots of the tracer and the exception. Any assistance in solving this would be greatly appreciated.
** Exception thrown by "com.pegarules.generated.pega_uiengine_pzskinfua.pzSkinMethodBody"