There are three separate issues in your report. Because of previous problems with changing the default user agent, I haven't made any further changes other than to update the FPR release number. This means that the site shouldn't enable incompatible features, but many sites will simply dismiss the browser as too old. That's why the User Agent field exists.
The Facebook issue is known. There is no current solution other than what you're doing. It is unlikely I will change this because of other problems with Facebook.
I can't replicate your issue with Paypal; I use it frequently. This may be a new change that hasn't been rolled out to all users.