Sorry you had a bad one on Monday. We were out there too but finished our ride before 11am and didn't have any issues with other riders. I definitely have had more bad days on Seymour though than Fromme. I think part of the problem is that there is shuttle access, 2 way connector trails that are relatively narrow and the occasional large group or mudbunny ride and you can start getting your flow interrupted pretty easily.
No solutions or ideas here really. Just to suggest that maybe we need a more detailed set of etiquette guidelines just for Seymour itself that align with a higher density of riders on a narrower ( and sometimes 2 way) trail network. Then post those guidelines in more places might be helpful.