Sap coming up through stain

My neighbor's deck was built in August 2022.  She stained it in May 2023, so plenty of time for wood to dry.  It was made with pressure-treated wood.  She used a semi-solid stain.  Not long after, sap started coming up under the stain on the stair steps, creating bubble-like protrusions filled with sap.  Looks horrible as some have burst open.  Is there a way to avoid this?  I'm asking because my house was built around same time, and I want to stain my deck and stairs.  I'm planning to use Restore-A-Deck three-step process with a semi-transparent stain.  I have not noticed any sap on my stairs or anywhere else.  Any advice would be most appreciated.  Thank you.