Confused about tense in synopsis (multiple POVs in diff time periods)

I submitted my synopsis for critique after doing one of the Guide to Literary Agent webinars. The feedback was really helpful, but one thing threw me off. He said it felt confusing b/c I went from telling the MCs story to "a long flashback involving her grandmother and great grandmother."

My novel is told from 3 POVs and two of the POVs are dead (the MC's grandma/great grandma). I thought I did a decent job at transitioning from the modern-day MC to the chapters written in the past, but guess not. I mention how MC finds her grandmother's diary and becomes obsessed with finding out this particular family secret, and how she finally learns the truth through the book. The next para starts with "When great grandma has a stroke and must move in with her daughter..."

I know the synopsis is supposed to be in present tense, but would it make it more clear that this is something MC is reading in the diary if I wrote something like "Through the dairy, MC learns that her great grandma had a stroke in xx year and had to move in..." instead of writing the flashbacks in present tense? Or is it a complete no-no to switch tenses in a synopsis? The synopsis is so confusing for me with the multiple POVs in different time periods...

Thanks!

Thanks - that's what I thought originally, but the critique gave me pause that maybe it was confusing the way I wrote it. Maybe adding in the year will help a bit like you did.