Hey sue181,
We’ve looked at this numerous times because of reports on forums, and ran internal gameplay sessions with automation; They’ve 100% dropped on each test session. We’ve poured through the data and code just to make sure as well.
I received my Crimson plans on the first set of bounties this season whereas my friend got theirs when we hit ~800 paragon. It’s a wide difference of chance, but I just want to make it clear, there is no bug with the drop % chance on the Crimson Plans.
I appreciate you reaching out about this and i hope you receive them soon.