This may or may not solve your problem, but I have experienced something similar with other social media scripts. Sometimes multiple scripts on a page clash- for whatever reason (bad coding, similar code). This can result in display errors in some or all browsers. It can also result in the script not functioning at all. For instance, the AdSense ads scripts can clash with other scripts, rendering other scripts non-functioning or causing the AdSense ads to display strangely.
I'm not surprised that the behavior changed. The time I had this problem, all was working fine for months after the scripts were installed. I suspect, my theory is, that because some of these scripts make calls back to their respective sites for code, that the code they are calling to can change. A modification/update of the code the script is calling in can cause the issue to begin.
My scripts were playing fine for months then all of a sudden the AdSense ads were displaying the wrong size. Then in another instance of clashing scripts the social media buttons stopped working. In another instance, display issues were occurring only in FireFox and only within a certain OS (I received a bug report from a site visitor). Facebook buttons were the source of an issue and I ended up removing it then ultimately replacing it with addthis. As I recall, for the Addthis clash, I believe I moved the code around on the page, from one location to another, and that seemed to have solved that instance.