The support is non-existing, they only blame you for all of the component issues. It is never the case the are wrong or there is a bug. This is the first developer I see that claims that his extension has no bugs at all.
You will simply waste your time and money with sh404.
It causes a lot of errors, breaks the work of other extensions (i.e. those dealing with Facebook) and doesn't solve any of the issues it claims. It slows the web site significantly and has a horrible user interface.
My advice is: STAY AWAY FROM SH404.
Let me clear this first: I am the one and only developer of sh404SEF, and I never claimed there was no bug in it. Aside from being a stupid thing to say, as every programmer knows, it would be pretty difficult to claim: if you just look at the changelog of each new version, we usually fix a bunch of them ;)
What we claim though is that when an actual bug is reported, we fix it, as quickly as we can.
I have searched this morning our support forum for threads dealing with "breaking other Facebook extensions", and couldn't find any that were not solved. And even the most recent one is from May 30 (more than 2 months ago). Haven't found any user name similar to what you are using here either.
If you feel like so, please contact me directly by email and provide me with a link to the support forum thread, so that I can review it personnally.
Now the only thing I can think of is if you are trying to use both sh404SEF Facebook (and other Social features) at the same time that you want to use another extension providing social buttons. You cannot do that: it's one or the other. The fix is simple: disable either the other extension or sh404SEF social feature.
Of course, if you disable sh404SEF social feature, you will loose its ability to hook up social buttons with analytics and provide usage data right in the admin panel of your site. Including for Pinterest buttons, which is something you can't even do with Google Analytics itself.
I won't comment on "causing a lot of errors", "doesn't solve any of the issues it claims", "horrible user interface" as you don't describe what you dislike. I do think that over the last 6 years quite a few Joomla! users have been of the opposite opinion, and some of them have said so right here fortunately.