Possible solutions
pyWorkPage was always a controversial practice even in Traditional UI… There are a few different ways, I honestly don’t know what rule/class context to use each. Sometimes primary works, some times caseInfo api works, most of the time TOP works. If anyone knows when to use what, I’d love a Constellation 101 on the topic 
- Primary Primary may not solve the issue (it sometimes does).
- caseInfo.content Using the caseInfo.content page can also solve the issue but the most common solve is using TOP.
- TOP page this predates Constellation, but the stateless nature of Constellation means TOP is the only way to traverse from data level to your case level.
- Understanding TOP and embedded page in pega - Knowledge Share - Pega Forums
- Pre & Post Processing for Embedded Data
- There’s a few examples of it in use, not with saveable datapages however they may help you.
- https://docs.pega.com/bundle/platform/page/platform/user-experience/validating-embedded-data-fields.html
- https://docs.pega.com/bundle/platform/page/platform/user-experience/marking-single-record-table.html
- https://docs.pega.com/bundle/platform/page/platform/user-experience/validating-total-amount-embedded-data-table.html
- https://docs.pega.com/bundle/platform/page/platform/user-experience/validating-unique-values-embedded-data-table.html